Arena?

Are random arenas popular?

Yes.

To get to higher levels of PvP (like HoH) in Guild Wars, you have to win a certain number of matches in Random Arena (RA) and Team Arena (TA). So, to get to other parts of PvP, you have to start in RA.

In that sense they are popular.

Yes and no. Random arena is considered just about the bottom of the barrel for pvp, although paradoxically most high end pvp guilds want you to have a decent rank for doing RA (and team arena) Tons of people do it, and it's a good way to go in and check a wacky build to see if it is effective, but it's often an intensely frustrating place as well since a lot of people start out pvping there and have no idea what to do.

RA is very popular, more popular then team arenas.