This probably doesn't fit entirely within the tactical isometric genre, but I just wanted to give a plug for the original Ogre Battle which is one of my favorite all time games.
Ogre Battle sits somewhere between a tactical RPG and a real-time strategy. Basically you're able to roll up a leader character in the beginning and then you're given a small group of 5 units. As you conquer world locations, you're able to recruit more and more units to build your army with.
Now the really cool thing about Ogre Battle is that it is actually quite easy to win the whole thing. Evil units like ghosts, demons, werewolves, black dragons and skeletons are the most powerful types in the game and they are also about the easiest to recruit. The catch is that, if you go the easy, "evil" route you will receive the worst of the 12 different endings in the game, and will also be unable to recruit the coolest secret units in the game.
For example, to win over the 4 high generals of the opposing army (which are very powerful and awesome), you must play the game in a very middle-of-the road, neutral manner. To get the 3 secret holy knights of the game (which are very very powerful), you have to play extremely good. There are many more easter eggs like this that can only be found if you play the game in a "good" way.
So the catch-22 is that to play the game as a "benevolent" leader, you have to purposefully bring out some of the weaker units to battle. Simply slaughtering the enemy with your powerful evil monsters will bring your reputation down and lose you the support of the people.
I've heard that Ogre Battle 64 is considered better by some people, but I disliked how slow the game got started in it and it feels far more "JPRGish" compared to the original. The original Ogre Battle has more of a western flair to it and gets you right into battle in the beginning.