I usually play Halo for the multi player, but the single player is also enjoyable for myself. Halo 2 was a bit meh, and Halo 3 was alright when it came to the single player mode but I think Reach outshines both of them. Also let me point out that I really haven't played Halo 1 especially the campaign. It's a bit darker, more ways to complete your mission, and the elites are back to being your enemies and not your melodramatic allies. As far as the story goes, it's Halo, I knew all of Noble team was going to die since Master Chief is the last Spartan, some junk about Cortana, blah blah.
I'm just glad I'm done with that dual weidling nonsense and have weapons actually worth something this time around. For example the needler in Reach is about as strong as two needlers in Halo 2. That's the way it should be. Also the pistol is worth something again. Hooray?
Also there's some ship missions, and they're okay. I was just waiting for Star Wolf to come out and say "I can't let you do that Noble Six". In short it's probably the best Halo campaign in years which is something.