Well, in all fairness my PS2 collection has grown enormously over the past year. I've been able to cash in on a number of great deals and pick up all sorts of classics for cheap. My Gamecube collection was much bigger than that one for the longest time, and it wasn't until recently that it was eclipsed. Really, it's only a matter of time until my NES collection eclipses it.
My N64 collection is still very much a work in progress. It's one of my all time favorite systems, and there are a ton of games that I still want to get. A lot of the games I had and loved growing up technically belonged to my brothers, so it's taking awhile to acquire all of the rarer N64 titles out there.
As for Neo Geo, it's not a system I had growing up, and I have yet to set my sights on starting to collect for it. I'm about due to expand to another system, but I haven't yet decided which it'll be.
Being that I am in the process of buying a house, my first priority is to take care of all those expenses before I do anything else. I'll probably use the buying downtime to finally set up the epic game room I've always dreamed of (pictures to come).