Nah, definitely not the only one. It's not mentioned as often as, say, Splinter Cell or MGS but it is still one of the core founders of the stealth genre. As for me, I played the crap out of the first game as a kid, even though I sucked at it until I was an adult. I remember playing it quite a bit at probably 10 FPS on my grandparents' Compaq Presario during some family gatherings and such.
I mean, the series got a reboot title in 2014. It's not exactly unknown, but yeah, it's not super prevalent in conversations these days, unfortunately. Speaking of that reboot, I remember being so hyped for it after reading about it in GameInformer, but didn't actually buy it until a couple years later. Personally, I don't know why people hated on it. Yeah, it played different from the first three, but I thought it was still a very solid, heavily atmospheric stealth game.