Summary: If you like REACH, you will love this. And the other way around. Though you are a very stripped down "solider" version of a Spartan, you still kick ass. This game is more methodical and takes much more planning, and logic. While it is just like all other Halo games, (unlike Halo Wars, yuck) you are very limited as far as weapons, health, etc. Making the game much more challenging and exciting.
Summary: New hero, new campaign makes Halo 3 ODST a must have for true Halo fans. Its like previous Halo titles that you know and love but its also a whole new experience with new characters to explore and use. This game will have you looking around every corner and exploring every area carefully, witch in my opinion makes for a more realistic experience.
Summary: Story is very well written in this game. It is well told, and well acted by Firefly and BSG veterans. It is really entertaining and one of the best parts of the game. However, it is told through flashbacks & is somewhat difficult to understand your first time through. You might be confused at times, but in the end, it all makes sense.