Originally Posted by Uncanny1
Thanos and Ultron have been in videos games. Kang the Conqueror? I would pick Marvel ' Morgan La Fey ' over Krang.
What video games? I've personally never seen Thanos in a game. Ultron and Kang were (very recently) in the Facebook Avengers Alliance
Thanos hasn't been in an issue of Avengers in the last 15 years (barring his appearance in the continuity light Avengers Assemble
series launched to captialize on the first film last year). I pretty confident in that claim but I could always be wrong. Kang had a major 16 issue
arc (#41-55 + annual) in 2002 where he destroyed Washington D.C. and conquered Earth. I know Thanos killed most of the Avengers once but Kang is no small threat either. I'm just arguing that he is much more important to Avengers' lore, specifically, than Thanos and thus more deserving of some big screen recognition.
As for Morgana Le Fay, she's an established threat too but we already had a magic threat in the first movie and she is relatively low on the list as far as recognizable villains go (granted the list is pretty short). I would argue that Thanos is really not that much of an Avengers threat but rather a universal one, like Galactus or even Doom. His cosmic nature makes him much better suited for another movie, like Guardians of the Galaxy (I wish!).