Figured this hasn't been done. What are popular brands or even specific parts where you live? Of course the market is vast so not everyone will be riding clone bikes but typically locals ride the same brand.
Here in Surrey , British Columbia , the most popular parts are ;
Colony BMX. Suuppeerr popular. Basically 75% of riders here , good or decent , have a part or more. They on my opinion are the leading brand here. A friend bought a complete Teddy complete and his other bike is like 40% colony.
Academy. They make completes and I don't know a whole bunch besides my LBS has alot of completes. I don't own a part but apparently for a "saving" brand they make good parts. I know a friend has some bars and he goes big and they last.
Macneil. Of course Macneil is a Canadian brand so they're big. Alot of sponsored riders both Pro and Flow are around the better parks among Vancouver.
Norco. Just a complete bike but they're Canadian too (95% sure) so of course you see alot.
Deluxe. Dirt Jump brand , they make cool stuff. A local is sponsored by them.
Division . Like a more unknown brand but they make a variety of parts.