Possibly the best multiplayer RTS on the 360, XBLA or otherwise!
Booty may seem overly simple on the surface, you sail your ship around capturing towns and upgrading them along with you ship while fighting off rival buccaneers. Dig deeper though and, like with any strategy game worth its salt, you have a game experience that requires you to go in with a plan of attack. If you can execute your plan better than your opponent(s) then you just might be the one to sail away with the treasure at game's end.
AoB comes with a fun set of 27 single-player challenges, but where it really shines is in online multiplayer. Form a team with a couple other scurvy dogs and battle it out to see who can rule the map. Teamwork is a key so come with mic enabled and be ready to work together with your mates.
I can't recommend this game enough. At the very least try out the demo which sets the bar with its 48 hours of LIVE play included. Take the plunge and you will quickly see that this game is worth the 800 points and a bottle of rum!