I would say Halo 3,because it has about 20 maps with gameplay that newbies can play with people their rank,but experineced players can play people their advanced skill level as well.Many possibilities in the game,many weapons,great enemies...
But I don't say that CoD 5 is bad,but it's just not so fun to play it after Modern Warfare with advanced weapons and everything...
I think that Halo 3 is a little better,but CoD 5 is a great game too.
It depends if you want a sci-fi theme or a WW2 theme, really, but id choose Halo 3 over COD:WaW, its alot more fun to play, and the custom games are great to have a bit of a laugh with a few friends
World at War is so much better. I can't help you out with Halo 3 because I have a PS3, but I think it's not a good game at all, so go with World at War.
I would say get WaW. Halo 3 was Probably the worse of the series, and had a weak storyline. WaW, had a good storyline, with some great events, thought it too was a bit bad at times (though the ending rocked!). Halo 3 does have some great online, however i found it was riddled with hackers and cheap-o-'s. WAW has a more "even" playing fieldd, along with more modes (i think) and a class system. It also has more rankings (650!) which will definitely keep you playing. WaW is also very active with DLC, have 2 Map-packs out, and a third coming out very shortly. Plus, WAW HAS ZOMBIE MODE!
CoD WaW is the better online game to me. You have to develope some skill to playing it. Halo 3 you just have to charge in then run away to let your shields replenish. Single player is about even, but I give CoD a slight edge.
