Sorry, can't agree. Almost everyone plays a Fender or a copy of a Fender. Not saying Gibson basses haven't been good, but it's clearly never been their focus market, and they don't seem to have a market share that even approaches that of Fender. Fender basses are ubiquitous. Thunderbirds, Explorers and SG's stand out more because hardly anyone plays them. I wouldn't call them iconic at all. Fender is one of the first choices every bass player makes - either for or against, they still make the choice. Gibson honestly never occurred to me, 25 years ago or since, while Peavey, Yamaha, ESP, Schector, etc. have all been contenders at some point, and none of them are iconic in any way either.
When I think Gibson, I think guitars only: Les Paul, Firebird, SG, Explorer. I don't consider them a strong bass *brand* despite the fact that many greats have played them, (well, I can think of one, Entwistle, and he used a Fender neck) and despite the possibility that they may be fine instruments, they just don't have the brand awareness that Fender has for bass players.