I would claim that riding style is more important than the last three. Agressive/offensive riders that attacks a lot and wins important races due to this are generally more popular than wheelsuckers and GC riders in the same format as Wiggins and similar riders.What I think makes a rider popular in general:
What makes me to like a rider:
- success first and foremost- some less successful riders might get more popular than they results would suggest but the riders with the biggest fanbases are pretty much exclusively big winners
- nationality- whether you like it or not it's a big factor for most people
- time of rising to the top- a rider who starts dominating against a bunch of well-liked riders will get more unpopular while a rider who stops the domination of a disliked rider will get more popular for example
- relatable life story
- some more random and superficial stuff than you would think.
My favorites the last 10-15 years are Gilbert, Nibali, Aru and to somewhat degree Cancellara and Contador. I didn't care much for Valverde, Gerrans, Wiggins, etc.
My new favorite is denitely Van der Poel. Still haven't found a new GC favorite.