DennisKirk.com is pretty good. Usually everything is at list price, but that is not uncommon.
Revzilla.com is pretty good, big selection, and usually lots of stuff in stock. They ship quick. They have a sister website Cycle Gear, same prices, same everything.
The little guy in the industry, that is also pretty good is motorcyclegear.com They sometimes have better prices than the others, but not always. I tend to compare prices. If I can, I buy from motorcyclegear.com.
For most items, if you compare prices, the price may vary by a couple of pennies as there seems to be manufacturer's agreements on minimum prices. If you want a deal you need to buy discontinued items and overstocks. There are a couple places that specialize in discontinued items and often have deals on lesser quality brands.
There are others, some specialize in more HD realated stuff. Others specialize in more offroad/dual sport/ADV touring stuff. But the 3 listed above will get you well outfitted and supply lots of stuff you didn't know you needed.
Sometimes you get lucky and get something like an Arai or Shoei or Schuberth helmet for a couple hundred dollars off, but it is usually an unpopular graphic or a discontinued item. Still top quality, and a great deal IF it fits.
For jackets and pants I prefer Rev'it, which is a Dutch brand or KLIM which is an American brand. FirstGear is a good modestly priced brand, but they have very limited designs and it seems like I'm seeing far lower availability over the past couple of years. Rev'it, Klim, Dianese make top quality PROTECTIVE gear and high prices. Dianese seems to make a lot of slim (European) cut clothing, which just doesn't fit me, but it is good stuff. Rev'it and Klim fit me. Boots from Sidi, Forma, Rev'it, Dianese, Alpinestars and several others are usually good. Forma being the discount brand of that group, but still good. Usually can find deals on many of these brands.
I seriously dislike Joe Rocket, Tourmaster, First Manufacturing and several others.