You can't beat the classics.
Story
-----
This game started it all. It started the Halo series, and set the standard for an FPS. One of the great things about Halo: Combat Evolved is the story. The story is a nice balance of character-driven-ness and unexpected plot points. The concept is simple: humans fight aliens. Sounds dull at first, but the story isn't actually all that simple. I won't spoil anything. Story: 9.5/10
-----
Graphics
-----
For its time, Halo: Combat Evolved had state-of-the-art visuals. On the PC, the game looks like it belongs on the Nintendo 64. But on the Xbox, it looks nice. Blocky at times, but overall, very nice. Graphics: 9/10, for its time.
-----
Gameplay
-----
The campaign is comprised of excruciatingly lengthy chapters progressed through a linear manner. Therefore, Metroid fans who plan to give Halo a first shot, don't try and sequence break. :P No seriously. Don't. There isn't even a sequence TO break in the first place. The chapters are divided up, so you have little freedom to explore. But that's forgivable; the game is amazingly enjoyable, particularly on campaign. The controls may seem like the usual FPS controls, but keep the fact that Halo practically introduced this "generic" control scheme in mind. If you like bosses, you're out of luck. Halo has no bosses. But that's forgivable too. The enemies are at a necessary difficulty, making the game suicide on Legendary and a breeze on Easy. Those who played Halo 3 first and think they're so bad that they'll try this out, bear in mind that ELITES ARE TOUGHER THAN BRUTES. Oh yeah. I went there. On Legendary, hell, even on Easy, Elites can take about five hits with melee attacks before their shields are wiped out, finally leaving them vulnerable. Their shields also recharge. And those are just blue Elites; with red and gold Elites, go ahead and add even more hits to that. Of course, as expected, nailing them in the back will immediately kill them. Brutes on Legendary on Halo 3 take three melee hits, and they're finished. Grunts in this game are tough and gutsy in comparison to the later Halo entries, as even when their Elite commander is assassinated by you, the Grunts stand and fight. Jackals are the same as they are in the later games, so expect nothing different. Hunters are asses until you figure out the trick to killing them: shoot them in the lower back with a Magnum. Instant kill. Drones aren't in the game, and neither are Brutes nor the Prophets. There are fewer weapons in this Halo than in Halo 2 and 3, but inhuman amounts of ammunition allowed on each weapon makes up for that. A good example of this is the Sniper: it allows four shots per clip, and can have a maximum of sixty bullets! The same with weapons goes for vehicles.
The multiplayer is boring when you go online with it, as every match you will find a hacker, a camper, a cheapshot, or a combination of any of those three. The maps are good, but the inability to play as an Elite hampers the fun of multiplayer. Gameplay: 9.5/10
-----
Sound
-----
All throughout the game, you will hear the familiar orchestrated tunes that define the Halo franchise. The sound effects are what you would expect from an FPS, and the voice acting is wonderful. Sound: 9/10
-----
Length/Replay Value
-----
Despite the campaign's enormous length, you will find it difficult to stop performing play-throughs of the campaign. The multiplayer will get old fast, though. Length/Replay Value: 9.7/10
-----
Fun Factor
-----
The campaign will keep you busy for quite a while, but as said, the multiplayer won't last very long unless you ARE one of the aforementioned hackers/campers/cheapshots. In which case, you will find yourself busting a gut each time you obliterate a pathetic n00b online. Fun Factor: 10/10
Overall: 9.9/10, superb. Halo: Combat Evolved is easily the best Halo title, and it will be a while before you are bored with it.
Ultimate Ridley out.