At www.ngemu.com there has been made a top 5 of the most popular emulators.
ePSXe is the best one but you will need to download graphics/sound/cd plugins. The best graphics plugins are the ones by pete, though it will depend on your hardware. I don't know which is the best plugin for sounds though, but you can look it up in the plugin list since all have a rating next to them.
I almost forgot: ePSXe will need a BIOS as well and to get that one you will need to dump/rip it from your OWN psx, getting it in any other way will be illegal. So don't ask us for giving a BIOS or pointing you out to one, that's against the rules.