Halo: great campaign, shitty multiplayer, rather sluggish physics engine.
Halo 2: shitty campaign, awesome multiplayer, awesome physics engine.
Halo 3: average campaign, average multiplayer, average physics engine.
For me, Halo brings back memories, but it's rather obsolete now, especially if you're looking for competitive play. Halo 2 was my favorite, but I'm probably just being biased, because it's one of the shooters I'm best at (I was level 50 when the game was initially released, and I eventually went down and maintained levels of 40-43.) Lots of glitching, with the double shots and BXRs and all.
Halo 3 just felt like a watered down version of Halo 2 where precision was no longer important, as if to make it more enjoyable to new players. You couldn't just overpower the other team with superior aim and BR skills anymore, so you had to rely on teamwork, in a very frustrating way.
