a while ago i sought a tool to make 2D sidescroller. i searched trough maybe 8 tools, also gamemaker, but landed here and now i use the sgdk 2.
i like it very much, though it gives me some tough moments
it is very mighty, i dare to say. if you are a little in programming, you will have not so much problems. i can't really script, but here all works pretty well. (because of the construction kit for making scripted behaviours and so on)
one other thing i very appreciate, the creator of sgdk and other helpful guys are almost every day here and answer questions. i was never at the gamemaker community, how is the "support" there?
you can make not just sidescrollers and platformers. there is a project sample for isometric games and another for a tetris clone. a top down perspective for a rpg wouldn't be an expenditure. i think it is very flexible there.