They were king with the desire/nexus one, however, they were the only good android manufacturer then, no one could compete (android wasn't "that" popular either then), in fact I can't even think of what android phone there was that could compete with it, then came the galaxy S1 (came rather late to the game though), I didn't like it, but iirc in the end it sold more and became more popular than the desire.
HTC's problem is not with the phones they make (there one series were fantastic really and easily stood up to the GS 3 overall, the desire HD and sensation were one of the biggest key factors to their downfall though [imo]), it is more to do with their silly decisions i.e.
- releasing all these difference versions of the current model, last time I checked there were at least 6 "S" devices and then releasing an improved version like 2 months later
- awful marketing/advertising, it is a bit better this time but still sucks
- phone names, phones feature names, Samsung have nailed this area and doesn't sound anywhere as confusing as the likes of HTC = desire, sensation, one S, X, V, XL and now the "one"
I have no doubt that it will be the same again this year with the one VS GS 4 i.e. GS 4 will have better specs overall and be a more "complete package", not necessarily a "better" phone and will sell millions more.
Just having a look at all the news site and pretty much every top article is to do with the GS 4/samsung, then had a look on gsmarena:
Phone isn't even announced yet! marketing + lots of hype = profit!