I've been very happy with Edge-Host.com. I got a great custom quote from them for a reseller account and support has been excellent. So far, I haven't experienced any downtime which is also supported by InternetSeer monitoring.
I am using Priority Colocation http://www.prioritycolocation.com
and have not had any problems with support or service. I got a custom quote for my needs and everything since then has been no problem at all.
The best is whoever has what you need at a price you can afford. Once you get that list, your 'short list,' you should come up with three, four, five questions that aren't in their FAQ's and do a presales inquiry. To me the answer isn't as important as the tone of their response... the way they talk to me and how they feel about the people at the other end of their keyboards.
Then do a search here, in the WebHostingTalk (WHT) forums. Go through your short list and find old and new threads. You'll get a snapshot of the their history, their reliability, who likes and dislike them, and so on.
Look up SplashHost.com and E-starr.com. I'm happy with both of them.