I don't have much to say about single player, it was fun enough and it holds up to the other ones well enough. I won't draw comparisons.
It's pretty hard to deny that the multiplayer is heavily influenced by Call of Duty, right down to the loading screen before matches with the developer name displayed in the corner, right down to the way the game tells you what team you're on before you start play, the way you unlock weapons, of course the loadouts, grenade indicator, built-in sprint, killcam, perks (some of which are taken directly from CoD), ordinance drops as a stand in for care packages, etc, etc.
The thing is, this isn't intrinsically a bad thing. It actually works amazingly and makes the game more fun than either CoD or past Halos, and it still plays exactly like Halo should. The elements that were taken from Call of Duty are actually extremely good ideas, and since the problems with them were worked out over the course of the various CoD installments, they're here fully balanced and not broken. Same thing with the armor abilities, which have been balanced and expanded on from their Reach counterparts. It just feels polished. And though the playlists haven't fleshed out at ALL yet and there are some annoying glitch-into-wall bugs that have yet to be fixed, I'm having more fun with this Halo then I've had since I got live and started playing Halo 3 five years ago.