Scrubs is the best of the list, but it isn't a DRAMA... so I had to vote for ER. I've only seen bits and pieces of Grey's and House... and I've not been thrilled.
I'm with Airmedic_8 - the first few seasons of ER were great... then it has gone downhill. I guess part of it is that after 6 or 7 seasons, they run out of original ideas.
Third Watch was good for the first few seasons, too... I can't wait until they get around to releasing the first season(s) on DVD.
i vote none of the above... it's EMERGENCY! hands down... you can't beat johnny gage and roy desoto in their dodge ram utility body for all of the exciting calls that we never get.
I don't watch TV, so I really can't vote. Medical dramas normally are so fake though, from what little I've seen, that they'd probably piss me off more than entertain me...