Aside from the combat system (and post-apocalyptic setting), I found very little that was similar to the RPGs. Small unit tactics (think X-Com or Jagged Alliance, but not as good, in my opinion). Throw in some vehicles and fairly linear maps, and you have Tactics. It just didn't grab me like the originals. But if you've got time, and enjoyed the combat of the first two, then I suggest trying out 2-3 levels. I _think_ I quit playing after I accidentally backed over a teammate, without having recently saved the game =) Or some other equally stupid move.
Edit: After reading back through the Gamespot review, I might have to dig it out and give it another shot. Take my preceeding paragraph as the ramblings of a disillusioned Fallout fanboy.