2, 3, Reach, 1. I'm not counting the online, just sp. If I add in ODST, it goes to:
2, ODST, 3, Reach, 1.
I liked Reach, but it was really on its own. I really wanted it to be a blatant book copy, and it wasn't. I like it, but mainly for the online (which I like best out of the series). It's a very hard question to answer.
Yeah, I was ranking them based just on the campaign too. I'm not that big into multiplayer games, though.