About the graphics, I don't think professional looking graphics are the most important thing. There's a video from Extra Credit addressing the graphics vs aesthetics here: http://www.penny-arcade.com/patv/episode/graphics-vs.-aesthetics
Having some sort of consistent and stand-out-ish visual style is the key, not necessarily the latest bump, specular, enviroment, and parallax mapping in your game. Well, that's what I think anyway.
Edit: Meant to give the example, besides minecraft, there's also world of warcraft which still to this day has relatively low-quality graphics, that are pretty stylish and have good aesthetics.