All of the brands that might be able to be judged as overrated have qualities that got them there in the first place.
To me a piece of gear can be considered to be overrated if people will buy it sight unseen without ever having done any direct comparisons. That's different of course from having enough experience with a given brand to buy sight unseen, but when I hear people tell someone to buy a certain brand with no idea of what the persons needs are or only because they've heard that it's the best, then you're definitely seeing a good example of being overrated.
Bass site I know, but a couple of great examples come from the guitar realm, in particular if you ask someone about an acoustic guitar and they say Martin or Gibson, or guitar amps they say Marshall, then that's an example of some great products that are generally overrated, particularly because there are some pretty poor products from all three of those brands to go along with their legendary successes as well.
This most definitely goes for Fender and Ampeg as well. The reason they're so well known is because of the great products they've given us, but when people blindly vote for them over any other option, then overrated. Anyway, I don't think that most of the users of Fender or Ampeg have stuck with them for the wrong reasons, so, not overrated, IMO.