I saw a bunch of VW powered aircraft at Oshkosh. Were there as many VW powered planes as there were RVs? Of course not, but there were several. Most of the Sonexes at Osh that I saw were VW powered. All of the Sonerai's that I saw were VW powered. The Thatcher CX4s were VW powered. The BK1 was VW powered. These are just the planes that I saw on the few days I was at Oshkosh.
One of the biggest reasons why you see a disproportionate number of RVs at Oshkosh and SnF is the same reason why you see a disproportionate number of Long-ezs at these events. both planes are excellent long cross-country machines. My bet is that 90% of all of the flying RVs and EZs in the lower 48 states could have reached Oshkosh in 1 day.
As another example. The Zenith STOL CH701 has an outstanding safety record, and is fairly popular. It is used around the world in missonary work. Yet there were only a handful of CH701s at Osh, but many more Zodiac 601XLs. Why? Is the CH701, which has only had 3 fatal accidents worldwide and actually used in a working enviorment inferior to the Zodiac 601XL? No. The problem is that the plane cruises at 70kts. It is a much bigger trek to fly something like that to Oshkosh or SnF from California, than it is to fly an EZ or an RV or a Lancair.
To put Oshkosh in perspective. There were just over 1,000 homebuilts at oshkosh. Over 450 of them were RVs. My bet is that if you added the EZs, the Lancairs, and other fast glass planes that would account for over 60% of the homebuilt fleet at Oshkosh. Are they superior to the biplanes? no. Are they faster and do the make cross countries easier? yes.