The gameplay in this game made halo 2's cliffhanger seem perfectly understandable (especially the Cortana level).

User Rating: 10 | Halo 3 X360
This war begins on the covenant flooded Pillar of Autumn. Master Chief defeating a whole flood and covenant armada. Now he finishes the fight with the help of sargent Johnson, his marines, the Arbiter, and his elites (Floodgate). This game from beginning to end was very exciting. From this gameplay you surely won't be disappointed if you like sci-fi first person shooters. Might I add that this game's story takes place immediately after the cliffhanger ending of Halo 2. Sargent Johnson asks where Cortana was and you take off on a look for her to make Halo 2's ending make perfect sense.
Halo 3 isn't all that challenging unless you play it on legendary by yourself. If you play this game alone things might be more fun if your a soloist, but for those who aren't; you can play the campaign with people or against people over xbox live. All in all Halo 3 is a really great game. The war from Halo: Combat Evolved to Halo 3 is very worth your while abd worth the time and money to play through and triumph. Get Halo 3 and finish the fight.