If pre-registration sales are down compared to C3, it isn't because of the location. It's because there isn't a new Star Wars movie coming out. The first three Celebrations happened right before the theatrical premieres of each prequel. C2 easily had many more attendees than C1, and C3 had close to twice as many as C2. (And that is why your lines to get into C3 were so bad lj. It's hard to get 40,000+ people into a convention smoothly when people start lining up hours before the doors open. I had a volunteer badge, so I just walked right in.
) C2's lines were horrible (my friend waited in line for 8 hours to get Carrie Fisher's autograph). But aside from the store line, C3 really wasn't that bad.