EZ Drummer 2.... it is so simple... it has limitations but those are what I really love.. I suffer from options anxiety! I have not upgraded to SD3 for this reason... I love minimalism!
If you don't like to tweak, EZ is the way to go. Just load it and load some midi-files and you're done. But I like to tweak so SD3 is right for me. And I agree with DamaianGrada, TPF is the best SDX so far. Suitable for anything from simple pop to death metal.