Recently, I've playing tons of Halo Reach. I'm a huge Halo fan, so I found myself easily engrossed in the game. As of right now I'm trying to defeat the game on Legendary, the hardest difficulty. And I must say, this game is much harder than the others! The AI are extremely smart and crafty, and each enemy unit gets stronger and smarter based on rank. My favorite part is in the level Exodus when... Really the whole level really. My least favorite part is the end of the level Pillar of Autumn, when you're stuck fighting about five or six Elite Zealots, the hardest units to fight in the game. So many restarts... But the ending is great, even though they tell you how it ends at the beining.
All-in-all, Halo Reach is an epic game.