I think you could get into Halo 3. It's not spacey really or super high tech. Humans still use lead bullets for ammo, for example... There are alien weapons sure, but they have relatively the same functions as their human equivilents.
You mention people jumping 20 feet in the air as an unlikeable aspect...really, it isn't 20 feet, it's more like 10, and it doesn't feel like it's some great height to jump, it feels normal.
It's different from Gears of War because (and let me just say that I love GoW as well as Halo)... 1) Halo is an FPS and not a third person over-the-shoulder pov, 2) it is not photo-realistic like GoW nearly is, 3) Halo multiplayer matches are much more intense in a more 'run-and-gun' aspect - GoW has lots of stand-offs, hiding, etc...yet both games do maintain a requirment of strategy and quick thinking (i.e. using your surroundings to your advantage).
I dunno how to convince you that it's good but...it sounds like you will be renting it anyway so you can decide for yourself then.
