Games that present a really great design/game play concept then give you just a taste of it... sucks.

RTS's that don't have building options. COH hit the spot with just the right balance.

LOTR: Battle for middlearth II. I enjoyed this game more than total war. Remember to try the demos before dropping the $.

And if you haven't tried Company of heroes, your missing out. It's not middle ages, but its arguably the best RTS ever made.

   Best thing to do is, check gamespot reviews. If a game has a high score, try the demo, most games have them. If you enjoy the demo, it's a good bet your going to enjoy the full game.

Also, if your just starting with PC games, you've missed ALOT of good stuff that you could probably buy for just about nothing. Again, check present reviews and that of the past, you have a ton of great gaming ahead of you.