Metal Mitch is absolutely right about Gene's playing style, blues/arpeggio scales walks in a lot of KISS songs; Strutter, Rock-n-Roll All Night, Love Gun are all good examples of that. Fun bass parts that make the song sound heavy, but not overbearing. Not especially hard to master, but fun to play.
Gene is the perfect fit for KISS' sound, but Getty Lee he is not. Does that make him any less of a bass player? IMO it does not. My dad, who played guitar in country bands for 40+ years, went to Nashville for a bit when he was younger to try to make it in the music biz as a studio musician. When he went there he learned a great lesson which he shared with me that puts everything in perspective. And he said, "Son, don't waste a bunch of time worrying about who is better than who. There is always going to be someone out there is better than you. The sooner you realize that, the better musician you will become. It's about making music and putting your personal feeling into the part you are playing." He proceeded to tell me about how when he went to work every day, he would pass people playing in the streets of Nashville for hat money that he felt were way better than him. They inspired him every day to better his playing. I quit worrying long ago about who was better than who because of this. I look at things more from the, "What can I learn from watching and listening to this person."