http://www.youtube.com/watch?v=_t2Haq1YcKY : I reccommend tubescreamer type
http://www.youtube.com/watch?v=M9Wrksipi_Q : I reccommend crunch box type
http://www.youtube.com/watch?v=CyEgIaBlCJE: I reccomend a good compressor and digital delay
http://www.youtube.com/watch?v=UO_84C3fpuI : I reccomend erm... ok gods of gain you guys will have to take over here
(how does he sing and play that riff at the same time i'll never figure out)
So, no be all and end all solution. If you play a mixture of styles you'll probably need a mixture of pedals.
Also, sometimes people have different perceptions on what works well with chords too. Some like to hear every string clearly, some like how the pedal force the notes interact with each other.
The tubescreamers tend to mash some of the notes together, but lots of people love them exactly for that. And you'll find the different variations make the notes interact slightly differently, some growl more, some are smoother, stuff like that.
The marshall style pedals give you that crunch while in a sense retaining string clarity. I dunno, it's kinda hard to define innit? Do you hear two strings or one note? It's definitely not one note, but is it clear? To me I just enjoy the crunch.