This discussion is fascinating because it has put 
some interesting ideas onto the table. I've 
thought of this question quite a bit recently as 
I've been deciding what series to collect from. 

I'd say history is the best predictor of the 
future, so we only have to look back at 
animations a half century ago, give or take a 
couple of decades. The value of cels is linked to 
a combination of how well made the films are, 
what barriers they broke when they were produced, 
and how rare the cels are. 

Although the Disney franchise comes to mind, not 
all of their animations were great. The greatest 
ones were timeles, had engaging stories, and top 
quality animation. The films make people watching 
them feel the same happiness, sadness, fear, and 
love as they did 50 years ago. 

I haven't seen that much anime compared to most 
of the people on this forum. However, I know 
Grave of the Fireflies will make people weep 50 
years from now. I also know that Kiki's will 
still be entertaining to children 50 years from 
now. 

The ones that don't break new ground, are mass 
produced formulas, and are not particularly well 
crafted will probably not see much appreciation. 
No flames please, but I can't imagine what the 
appeal will be for Pokemon, DBZ, or TM a half 
centry from now. 

For what it's worth, I don't have cels from any 
of the ones I've mentioned so I have no vested 
interest (yet :).

- Chi