I am sure "best" and "most popular" have been discussed many times.
I see that Rapidshare" gets a lot of traffic.
Would this be the "most popular" host site available ??
I would make a list of sites you download from.
if your files you need are large, use the site that has what you need.
for small files use "free account" if you regisiter for a free account on most sites,
you may get cut in waiting time.
if your trafic is large then you may need two or more paid accounts.
I have megaupload & rapid accounts mostly for film & music.