I think this top ten list should be more dealer based and not national auction house focused as people already have their opinions of them as they are huge and well known.
As a separate category, Here is my ranking of the auction houses.
#1 I love buying Heritage CGC books, Awesome customer service, very rarely do they ever make mistakes, when they do they bend over backwards for you. They even ship me books now before I pay for them based on my track record! WOW! Great deals can be found if you scour the big event auctions for hours and hours and watch the live auction to avoid being sniped in the last second with a lousy cut bid. However, why on earth would you sell your books there with 3.5 times the commission as other sites? (buyer and sellers fees combined)
Heritage have great inventory if you're a buyer, but selling on there is ridiculous. You'd nett 30% less than what a buyer is prepared to pay after all the fees are added to the hammer price. I have however got great deals on Heritage - especially in the Sunday auctions and their service is exceptional.
BrontyBronty You know that guy that shows up an hour early for parties? Yah. I'm him.
Plug for worldwide comics!
I've never really bought much from major dealers before; always avoiding it as I've always been disappointed with the transaction.
I did just order a book from WW and the service (I asked questions by email) was outstanding. Between actually a fair price and the HUGE scan on the website and the great service, its been an outstanding experience so far and not what I was expecting!