yes, but that's like saying the beatles or elvis weren't influential because they weren't the first people to make pop music.
if you want to explore the legacy side of things and look at the games that basically built the groundwork for the MMO genre then you're clearly looking at ultima online and everquest... but since WoW is not only the first MMO that a larger majority of MMO players experienced but also the game by which the current market is most heavily influenced by, it's not unreasonable or inaccurate to say the current MMo genre is defined by WoW.