I'd say go with Brawl, especially if you have a buddy or 2, or 3, to play with. I can guarantee you will be playing that game until the next iteration comes out, if you like it . Same with MK (I personally like Brawl more).
Tag(thx fkusumot) - "Yet again I completely fail to see your point..."
HD vs Wii, PC vs HD: http://www.vgchartz.com/forum/thread.php?id=93374
Why Regenerating Health is a crap game mechanic: http://gamrconnect.vgchartz.com/post.php?id=3986420
gamrReview's broken review scores: http://gamrconnect.vgchartz.com/post.php?id=4170835