Despite dated graphics, a short campaign, and somewhat flawed multilayer, Halo 3 still delivers.
Single Player: Halo 2 left a really bad taste in my mouth, so I was eager to see what the campaign would be like in this. The campaign is short, for normal about 6 hours. While not as good as Combat Evolved, it is still really good, and a lot better than Halo 2. I still need to go through and get all the skulls, and I'm sure I'll be playing the metagame with my friends for a while. While it's still the old Halo gameplay, it's still really fun. My only complaints besides the length for the campaign would be the graphics and story. I've been raving over Bioshock for the past month or so, and when I played this I thought "What a lame story!" and "This is next gen graphics?" Let's face it, the story is unoriginal, and not that compelling. And for the graphics, it does look like Halo 2.5. I was really impressed by the lighting though, it looks beautiful. Overall, the single player is great and all, but I wouldn't buy it if you didn't have Xbox Live.
Multiplayer:
Did you really buy Halo 3 to finish the fight? No, we all bought it for the multiplayer...and for good reasons. The multiplayer is really, really fun. With the forge and custom games, the possibilities are endless. There's nothing more fun then just screwing around in forge and making a custom game, and then playing it with your friends that night. The co-op is great too, this weekend I'll be playing the whole game on legendary with three games, and that's what makes it fun. The bad part about the mutliplayer though is the matchmaking. Yes, it's fun to find people your level, beat them, and then rank up...but it gets old. I played matchmaking most of today, and I'm sick of it now. I kept on getting the same game types, on the same maps, and it gets old. I can't tell you how many shotty snipers I played today! I still look forward to ranking up even more though.
Overall:
If you have Xbox Live, or a lot of friends, this is a must buy. If you're looking for a good single play and story, it's a decent rental.