Before I begin "reviewing" Halo 3, let me start by saying how much I enjoyed Halo : Combat Evolved back in the early 00's. I never actually owned a Xbox, so I didn't play as much as I would have had I owned one. But all my friends did have one, so I must have played something between 15 and 20 hours. And from what I can remember, it was a very, very entertaining game, even if I couldn't have predicted the juggernaut the series became. It my personal Best games of All-Time list, I gave it a solid 9.2, good enough for 75th place, ahead of games like Killzone 2 and God of War 2.
Judging by the vast number of positive reviews the game gathered, I thought I was in for a thrilling ride. It turns out I was very much mistaken...
First off, the gameplay is pretty average. Controls are not precise, and the whole thing just feels wrong. At first I thought it was because I was used to playing games, and especially shooters, with a PS3 controller. It played a role, but not that much, because I'm currently playing Metro 2033, and while I'm still struggling a little bit with the controller, it plays infintely better than Halo 3. And I just finished Gears of War, another old 360 game, and the gameplay was excellent, so were the controls. However I look at it, gameplay was disappointing.
(I must say though that a few of the weapons were pretty cool to handle and felt original compared to what we see in most shooters.)
Now let's talk storyline. Granted, I didn't play Halo 2 and I didn't have much of an idea what was going on early on in Halo 3, and even halfway through much of it didn't make sense. That's not a good sign. A good sequel should be balanced enough so longtime fans are happy to see how it's linked to the wider story-arc, and newcomers aren't feeling completely lost. I felt Halo 3 missed that totally. And the missions were pretty damn boring for the most part. I didn't feel the urge or the need to complete them.
I won't comment much on the graphics of the game, since it's half-a-decade old and I might be biased against my will, especially since I'm currently playing Arkham City and Forza 4 and have just finished Uncharted 3. It's perfectly normal that Halo 3 can't stand up to what we see today. I'll just say that the game looks very "childish" when compared to other FPSs like Killzone, Call of Duty, Battlefield or even Halo Reach (from what I've seen in gameplay video).
Overall then, Halo 3 was a major disappointment for me. Though I'm sure the online was good enough to notch a few extra points, I don't think I would've been tempted to even try it after the mediocre campaign.
EDIT : The more I think about it, I cannot comprehend why gaming websites such as GameSpot gave it a 9.5. Then again, it's hard to trust that particular website, especially when they give high scores to wildly unoriginal sequels like MW2 (it had an awful campaign and copycat multiplayer), then gives 7.5 to Skyward Sword, widely recognized as one of the best Zelda games ever, on par with OoT which is still the highest-rated game ever. Astoundingly illogical, I know.