this question is hard to answer because it depends on what type of info you are looking for, whether size and # of co-locations or sheer volume of throughput they handle, or are you looking for a security specialty?
everyone has heard of RackSpace.com. they have been in business for 10 years and specialize in custom hosting packages. whether you need your own server or just a server running on a virtual session. windows, linux, etc.
whereas <a href=”http://www.gramtel.net/content/Home.aspx”>Grammtel</a> here in Indiana specializes in uptime and security. they have a locked down facility with biometric entrance security. the building is fed by multiple backup generators and also has fiber coming in from different directions and from different vendors so if an artery gets cut they will not go down.
as far as best, it is hard to tell because there are several sources that say “here is a top 10 list over the last year of the best web hosts”. and each list is different. some don’t even have the same entries in the top ten.
I use 1and1.com for my host for a website that I design for a hunting group out of Michigan and have never had any problems or downtime from them.