Small Unit Tactics game

Forgot about Rainbow Six -- I think the last one I played that I really enjoyed was Raven Shield. The original Ghost Recon was really nice too (I never played any of the others past that one so I don't know if they hold up to the same standard). If you (OP) wants FPS/third-person and real-time, both of these titles are excellent for squad-based tactics.

and +1 to the mentions of XCOM too.

+1

In the original X-com game, you could have squads of up to 26 on a mission if I remember correctly. But it's not like you'd move more than, say, 6 of them at a time.

Despite what I said above, I'd highly recommend the old X-com games if you can take the bad UI, steep learning curve, and the fact that you have to run it through Dosbox (this last point can be rectified by using Openxcom). Although the new XCOM is polished and looks shiny, I can honestly say I've had more fun playing the originals.

But if you want a game with good graphics, the new XCOM is pretty solid, as well.