Um, actually, yes, Ampeg does make the "best" amps. Just like with Fender basses, everyone who doesn't like to use them tries to explain away their continued popularity over the decades by saying they're "widespread" and in a lot of stores. And why do you think they're in a lot of stores? Because people like them enough to buy them. If people weren't still buying them in droves, no store would carry them regardless of their history.
So glad to hear such an unbiased and unclouded perspective from an Ampeg endorser, lol.
Seriously though, don't confuse "most widespread" with "best", as they are without a doubt 2 very different things. Fender? LOL. Fender is closer to the worst than the best. The vast majority of Fenders basses (and guitars) I've played in my life just feel totally slapped together, with no attention paid to construction, setup, etc... Now, the best ones are really special, sure, but they basically bank on their reputation and economies of scale (and outsourcing to third world countries) to maintain their market share. Do you think if you could get a Ken Smith, Alembic, etc... for the same price as a Fender that they would still have such a huge presence? HIGHLY doubtful. And also, if 2 products are roughly equally as good and cost roughly the same, the one that is more accessible is the one that will get bought. Just look at GC. They carry fewer and fewer brands all the time, so it's no wonder most people play Fender, Ibanez, maybe a MM, etc... and Ampeg, GK, Markbass, and Mesa amps.
As far as Ampeg, what exactly makes them "the best"? Specs? No. Features? No. Weight? No. Price? No. Build quality? No. Tone? For some people, sure, for others no. Their crowning achievement is something they designed 40 years ago. And there seem to be vast periods of their history where people say "yeah, don't get any of that stuff".
I'm not saying they suck, they do make some good stuff. But if you had a legitimate claim that they're "the best" your argument would have included some or all of those categories above rather than basically just saying "they're everywhere!". To compare to home audio stuff, I'm sure way more people have Realistic (aka Radio Shack) stereo components than McIntosh, but McIntosh is better in every single conceivable way, except in terms of price (as long as you don't consider value for your $) and accessibility.
Bottom line, when making purchases, people have all kinds of things to consider, including the ones I mentioned above, but the final decision is going to come down to money and availability, which work against each other. So if you have more money, availability isn't as big an issue and vice versa.