This is a list of SRPG and TBS games with a high level of strategic depth, variety, and difficulty. This is not a comprehensive list but it's a good start. If all you've ever played is Final Fantasy Tactics, Disgaea, and Idea Factory titles, the challenges on this list will be a good reminder of how skilled (or not) you are at the "strategy" portion of the SRPG (or turn based tactical level strategy) genre. All of the games listed cannot be trivialized by stat grinding, excessive save/loading, preorder bonuses, etc. That's right - none of these challenges can be overcome by grinding.
All of the games listed are developer provided challenges, not player defined challenges. That means the challenge is hard coded into the game by the developer and not something imagined up by a player to make up for a developer that didn't balance their game or add an effective scoring system.
Fire Emblem Thracia 776 (SNES): SSS Rank.
One of the last games released on the SNES in 1999, this Fire Emblem release was aimed squarely at hardcore strategy fans. Just clearing the game with its varied challenges is difficult, but there are also rankings based on speed. The highest ranking of SSS requires you to complete the entire game in 179 turns or less, an insane number considering the length of the game. Only by studying the game inside out, formulating a comprehensive plan, and relying on some luck will a player ever hope to accomplish this brain twisting challenge. There are more than a few large maps where you are expected to complete the chapter in 1-2 turns at most. Add on to that a wide variety of mission conditions and stats like unit fatigue that ups the strategic depth and variety. It takes a small novels worth of text just to describe how to do this one.
Game Boy Wars Advance 1+2 (GBA): Highest score on every mission.
This is the Japanese release of Advance Wars 1&2 on a single cartridge. Advance Wars features the Advance Campaign, a mode far beyond the normal campaign difficulty. There are rankings for each level based on how fast you completed each mission. Most of these rankings require precise strategies where every action must be optimal or you'll fail. In quite a few missions you must scramble to capture an enemy HQ while using most of your army as disposable cannon fodder to distract or slow down your opponent. You must understand the game, every unit, and the AI rules inside out. There's also Advance Wars 2 on the same cart that has a Hard Campaign that is not as difficult to get perfect scores on, but still above average. Both games also feature a War Room with single scenarios requiring further grey matter engagement to get the highest scores.
Panzer Tactics DS (DS): 3 star rating and all objectives on every mission.
This is a historical hex based wargame for the DS. This SRPG follows in the footsteps of classic SSI series like Panzer General and Steel Batillion, and the top Japanese wargame sim Daisenryaku by Systemsoft. While I don't have a lot of experience with PC wargames, I hope this sort of makes up for it. The rules are complex, there are dozens of units belonging to different nations, and there is a speed based scoring system and secondary objectives to be completed. Since this is an SRPG you'll also be challenged to keep your army and generals alive and gaining levels while still achieving the best score and objectives. Levels are varied and strategic requiring you to study each mission carefully for a chance at success.
Super Robot Taisen Z (PS2): All skill points on EX-Hard mode.
The most difficult of the Super Robot Taisen series. In this games EX-Hard mode, not only do your opponents get a huge stat boost, but the game forbids you from upgrading your pilots and mechs and from buying any new gear. This is more difficult than other Super Robot series EX-Hard modes where you're allowed to upgrade your pilots and carry pilot points from a previous playthrough. On top of that there are skill points to be achieved that require a high level of specific strategy for each mission. They're called skill points, you need skill to get them (especially on EX-Hard). It's even more complicated when you look at the sheer size of the roster - you'll be getting familiar with armies worth of mechs and pilots. The game features units placed into groups of 3 that can take on different formations and fight other enemy groups of 3, significantly increasing the strategic difficulty for each combat encounter. I should also mention the Super Robot Taisen Z Special Disc missions, which can all be played on EX-Hard as well.
Elven Legacy and Ranger, Siege, Magic expansions (PC): All Gold medals on Hard difficulty.
A solid SRPG that features 3 difficulty modes and medals awarded for performance, usually turns taken. Getting a gold medal on all Hard difficulty missions requires efficient general strategy and mission specific strategies. This may not be the most difficult PC SRPG out there, but at least there's a PC game on the list. There's lots to figure out for each mission on top of knowing all the standard SRPG fundamentals like unit management, XP distribution, efficient positioning, class strengths and weaknesses, etc. Even on Easy mode the game is quite a challenge for the average or unskilled gamer, as evidenced by almost every review on the internet complaining about the difficulty on easy with bronze medals. If the reviewers even bothered to mention hard mode and gold medals, they deemed it impossible or incomprehensible. Want to prove them wrong? Pick up this game and rub those brain cells together.
Knights in the Nightmare (PSP): SSS rank on most missions on Nightmare mode.
Not strictly an SRPG, it's more of a mix between SRPG, shoot em up, and RTS. Either way, though, the game rules are certainly complex, as evidenced by the long tutorial and high learning curve due to the large amount of unusual mechanics. It's unlike any other SRPG out there. There's also a ranking system that goes up to SSS and a Nightmare difficulty, just so you can prove how amazing you are at simultaneously commanding units, switching phases, dodging bullets, selecting weapons, and reading tiny sized roulette wheels. I chose the PSP version because it's even more complex and difficult with multiple wisp states and weapons spread to the 4 corners of the screen.
R-Type Command (PSP): High scores on every mission.
This SRPG features an open ended scoring system that rewards optimal strategies. Getting a very high score requires lots of planning and strategy, which you can then compare with your friends scores and check whose is larger. This is the basis of video games, folks! The campaign is above average in difficulty even with low scores. Its sequel, R-Type Tactics II, is even more difficult, with the same scoring system, but likely won't be ported to NA due to poor R-Type Command sales (shame on you).
Fire Emblem: Rekka no Ken(GBA): Hector Hard mode S rank.
Believe it or not the Japanese version is more difficult than the US version, which is why I am listing the Japanese version here. Fire Emblem is a classic SRPG series known for its permadeath, lack of save/reloads, and frenzied fanbase (just mention the words tier list and watch their heads explode). Getting an S rank on Hector Hard mode requires a difficult balance between 5 separate scoring factors, turns taken, units lost, exp gained, attack/kill ratio, and funds. In true strategy style, those factors work against eachother forcing you to make difficult choices like whether to enter optional chapters, and finding the optimal balance between rushing through a chapter or slowing down for more XP and loot.
Valkyrie Profile: Covenant of the Plume (DS): Kill all realmstalkers in every mission.
A difficult challenge awaits in this DS SRPG. If you choose to ignore the overkill/sin quota in a mission, the developers throw 2-3 boss-level realmstalker enemies at your party on top of whatever else is on the map. This is made even more difficult by the fact that you won't have overkill bonus loot to rely on. There's plenty of strategic challenge to be had figuring out how to take out the powerful realmstalkers and live through it while being undergeared and underpowered. Of course, most people who played this game couldn't even conceive that killing the realmstalkers was possible, due to lacking that all important video gaming factor called skill. Well now that you know it's possible, go on and try it.
Fire Emblem: Heroes of Light and Shadow: Lunatic Reverse, A ranks
While this newest Fire Emblem DS entry suffers from some difficulty-reducing features like the WiFi shop, Everybody's Situation, and a rank system that only goes up to A, it still deserves mention here as Lunatic Reverse difficulty packs quite a punch even if you do absolutely everything you can (short of cheating, of course) to make it easier.
realistic hex based wargame SRPG/TBS much like the classic SSI games
and others that followed it such as Steel Panthers World at War and
WinSP WW2. It's nearly unrivalled in strategic depth, with its large
rulebook, dozens of playable nations, and hundreds of unit types. The
missions are lengthy and difficult and there's also a scoring system.
As the title implies, Systemsoft has been working on the Daisenryaku
series since 1987 and they have had a good 22 years experience behind
their claim that this is a perfectly balanced title with tons of
strategic content to create and master. These sorts of games have real
strategic depth because you're required to learn every facet of the
games depth in order to master it - it's not like FFT or Disgaea where
you can just slap together whatever party you want and run all over your
Panzer Corps: Decisive victory on the hardest difficulty mode (where possible) + weather, supply, and fog enabled.
Gungnir: Masou no Gunshin to Eiyuu Sensou nightmare mode w/ 3 star rank.
Battle Academy. Highest difficulty mode, Enhanced AI. Earn all achievements on a single run of a mission, for every mission.
Daisenryaku Perfect: Senjou no Hasha
X-COM: Enemy Unknown Impossible/Ironman
Field of Glory