The memory market has certainly changed rapidly in recent times.
Around the launch of P4 and AMD Bartons your choice for top end RAM was pretty much something from either Crucial or Corsair. With the Socket 775 and AM2 platform the market became swamped with manufacturers all providing different solutions to the same thing. To the regular Crucial and Corsair we also saw OCZ, Geil etc., all gaining a foothold in enthusiast rigs.
With the move to triple-channel on the LGA1366 platform Corsair pretty much became the de facto manufacturer with the XMS RAM for the average user and Dominator for the enthusiast.