GET THOSE JETPACKS ON !
Halo Reach can be described with 2 words : Simply Awesome. You're 1 of 4 spartan 3s and you're fighting a losing battle, that alone should get you hyped up about the game. Now with an awesome arsenal of armor abilities, the competition just got a bit harder. Rain death from above with you jet pack, set traps with a hologram, or turn yourself invincible with armor lock.
The Combat is similar to that of Halo 3 and Halo ODST, and you're fighting the covenant again. The single player campaign is a gem but what keeps you hyped up is the multiplayer. You cant go airborne and just exit and expect to land safely, the fall damage keeps people from just sky-rocketing to the moon to regenerate health and then go back when they're good and ready, plus a capture the hill with all your teammates stocked with armor lock is a really fun experience, that is being fun for you and incredibly annoying for the opposing team.
Halo Reach is definitely a most-buy, you'll love the campaign and you'll never get bored of the multiplayer.