While they're well done at times, I think people should stray away from copying official art from games in pencil, as they should draw their own compositions instead of someone else's.
As for the other two, I just think you need to brush up on anatomy a bit, I suggest reading up on Burne Hogarth, Andrew Loomis, and Joseph Sheppard.
Burne Hogarth has helped me the most recently, his books are really useful for coming up with dynamic poses and anatomy. His ability to draw hands is amazing.
Andrew Loomis is also another great instructor to help you start, his faces especially are really nice.
Joseph Sheppard uses a more classical sense of anatomy, his figures have a lot of mass to them, as opposed to Hogarth's (while they have mass, they're more superheroic.)
You can register for a free account at Scribd.com and you can download any books for free, it has the complete Loomis collection, and all of the Hogarth stuff you'll need.
Hope this helps.

-Deimos-remus