I really enjoyed Mass Effect.....been out a while though, so you have probably played it already I'm guessing.

If you have a 360 and ten dollars to spare, you can get a decent three weeks to four weeks out of Chromehounds. Still a pretty nice population that plays, a lot of Japanese. The game will only last you three to four weeks because it's horribly imbalanced, sadly. I'd still be playing it if not for the fact that splash damage weapons are more OP than Runekeepers armed with Gatling Guns that shoot a thousand nukes per second.

But you'll have fun building and balancing mechs and trying them out for a few weeks and the variety in the various MP things you can do along with map credit quests (which flip areas of the map towards different factions) reminds me somewhat of playing in the 'moors.

Not really the genre you are asking about but two solid tactical wargames that I would recommend by this company:
http://www.battlefront.com/

This is a modern era Syria (pseudo Iraq) wargame
Combat Mission:Shock Force
http://www.battlefront.com/index.php?op ... Itemid=252
-Marines expansion presently and British army expansion to come

WW2 North African Desert
Theatre of War 2
http://www.battlefront.com/index.php?op ... Itemid=273

Both games have high detail and levels of realism, as an ex-AJ I highly recommend them both if you like attention to detail in physics, graphics and a certain amount of "believability".
Sometimes they arent a lot of fun as these arent fps type games but there is definately an achievement factor especially in the higher AI settings.
Some great expansions and player made add-ons for both these games as well.

They have another good title which I havent tried since its original
TacOps4
http://www.battlefront.com/index.php?op ... Itemid=163
US Army uses it for training.
I have used TacOps1 which is pretty old now but was interesting.