Pete's solo stuff was good, but I don't think he wouldv'e ever left the ground if not for the Who, Roger Daltrey, John Entwistle, and Keith Moon. I'm sure it's easy for him to have regrets now that he has plenty in the bank, like DA69RT GT said.
And without the Who he very well just could have never made a name for himself on his own. The Who, just like all other mega successful rock bands from that era had the opportunity to showcase all of their members who all were very famous and successful. Look at the king of them all, The Beatles. Every member of the Beatles were extremely successful on their own. There are several "pioneering" rock acts from the 60's who were very successful.