Let me first say I'm enjoying XCom. But it is very dumbed down, I'm afraid.
1. No stats. Original had strength, health, two kinds of accuracy, stamina, reactions, and more...
2. Reactions in the originals were based on a sliding scale of how much you moved in that turn and how many TUs you had left as a % of your total. Reactions in this new one are always on or always off.
3. You always get your Skyranger and *all your squad equipment* back even if your entire squad gets wiped out.
4. You can't pick up stuff on the ground.
5. You soldiers don't have an inventory.
6. Only one base.
7. You can't shoot walls, vehicles or terrain objects except accidentally.
8. There's no incendiary weapons (I don't think)
9. Fire doesn't spread.
10. No electro flares (portable light sources).
11. Smoke doesn't affect line of sight (which is very weird).
12. Grenades never miss

13. Darkness doesn't appear to affect line of sight (my guys can see just as far, I think, at night). Nightime appears to be cosmetic only.
There's probably more.