Heroes of Might and Magic III might be worth looking at. It's turn-based fantasy with a pretty solid AI.

Rather like Total War, it has a strategic level in which you build, recruit and move your armies then it has tactical battles when armies meet. The strategic maps are fun with lots of "goodies" to gather (items, power ups etc) and explore. A big part of it is levelling up your generals, allowing interesting specialisms in combat and magic. Unlike TW, the tactical battles are rather simple affairs - 7 stats max per side (although a unit may have 1000s of "men" stacked in it) and a pretty abstract Chess-like hexagonal map. A very nice feature is that the battles are brisk, so that small skirmishes are over in seconds. Even more epic battles can be emotionally gruelling but over in a five minutes or so. Overall, it's got the classic TBS "just one more turn" feel but without bogging down late game as most traditional 4X games do. (You can never have more than 8 field armies, IIRC, and typically have only a few cities to manage.)

The strategic AI is pretty basic but strikingly effective. The AI tends to designate a main stack and build that up, using it ruthlessly to crush you. It avoids putting its stacks within reach of any stacks of yours that could defeat it. Those two simple principles translate into a rather effective AI - RTW/M2TW could be so much improved if they followed them. The difficulty levels include some pretty big AI resource advantages, so you can be challenged.

The battlefield AI does a reasonable job given the complexity of the battles (many units have special attacks, generals can use magic to great effect etc). I would rank HommIII alongside Civ as having very good AI. By clever sequencing of attacks, judicious use of magic and smart targetting, you can win against the odds, but probably not as easily as in TW and you do feel you've earned it.

Homm is based around strategic maps - called scenarios - some of which may be linked into campaigns. However, the scenarios are often big enough and open enough that you don't need to worry about the campaigns. There are many user created maps - my favorite is "Middle Earth (allies)" which is a brilliant representation of the War of the Ring. It has an editor - it may have a random map generator, but if so, I would not bother with it. A well constructed map is a thing to be savoured.

Nowadays you can get Homm III Complete for a very good price, as it is an old game (2D although I find the graphics nice and the music very good). It comes with two useful expansions included.

Don't be seduced by the flashier graphics of HommIV and HommV - they are but shadows of Homm3. The AI is much weaker (HommIV is broken) and they lose the fast pace of the predecessor and cease to be fun.