My opinion (being a Hamilton fan) is that Button clearly out-drove him over the course of 2011. Button's 2nd half of the season was very impressive and he generally got the most of out the car. Hamilton could have often matched or beaten him but made far too many mistakes or was unlucky, or careless - whatever you want to call it.
You've got to look at qualifying sessions such as Monaco, Singapore, Suzuka and India as times where Lewis really should have been higher up on the grid and was not generally because of issues during Q3. In Monaco, Singapore and Suzuka you seriously have to question what his side of the garage was playing at and at India you have to question Lewis' mind set in practice. Is it not slightly coincidental and ironic that at ALL 4 of these races Lewis ended up crashing with Massa. Had his qualifying gone as it should (and even been on pole potentially 2 or 3 times) then he would have been no where near Massa.
2011 was a strange season for Lewis and Button just stuck the knife in and showed up all his mistakes by often driving flawlessly with calculated decisions. When it comes down to it though Lewis is still faster than Jenson - I think Jenson even knows this deep down. But Lewis showed remarkable weaknesses during 2011 that compared to Vettel make him look mediocre at times. I don't think Lewis will ever be able to have the same mindset as Vettel - I can't imagine Lewis ever winning near all the races in the season like Vettel did. He just somehow always manages to make things difficult - almost a trait of the English/British in sport in general. But without a doubt, on his day Hamilton is still untouchable and I still believe he has the most talent of any current driver.
Interesting on what Alonso had to say the other day:-
http://www.yallaf1.com/2012/01/18/alonso-vettel-still-slightly-below-the-level-of-hamilton/
I think 2012 will be very interesting.