Probably Asia will be the first association to his name.

But he was part of many groups, some of which are really classics: (from Wiki)

Associated acts Mogul Thrash, Family, King Crimson, Roxy Music, Uriah Heep, U.K., Jack-Knife, Wishbone Ash, Asia, Phenomena, Renaissance, Qango, Brian Eno, Ayreon

I saw him with the reunited Asia in 2010 or 2011, one of the better concerts of groups famous last millenium...

You might be surprized about the scope of him:
https://en.wikipedia.org/wiki/John_Wetton
http://www.rollingstone.com/music/news/asia-co-founder-king-crimson-member-john-wetton-dead-at-67-w464089