there were so many 'waves', so many years apart, that I have a hard time lumping them all together.
aol and yahoo, maybe. aol was much earlier, but they both hit max valuation at around the same 2000-01 period.
myspace hit max valuation at 05-06. 5 years might as well have been a century at that point in history with the amount of flux in that industry.
my first wave was the tail end of BBSs and the beginning of the walled gardens of compuserve and aol. a bit later came The Palace, The Well, and various other (incredibly formative and impactful) social cliques.
The social aspects was what separated the 'waves' for me, and the gradual shift from an idealist concept to something more corporate.