To me one of the most important aspects of a town is a park. What I do like in SV is the nice size Central Park. It is in the center of the town, nice size, and has a little bit for all; swings for the kids (although generally adults are on them), chess, picnic tables and plenty of grassy spots to spread out a blanket for a picnic and not step on anyone.
There are few nice size lots in AP, 40 x 40 or even bigger. Not enough good males either but you can't have everything, I created a spouse for my sim, now I just have to find ones for offspring.
RV is horrible for a park, the only one that fits is the Dogwood one which doesn't really have a place for adults, it is too cramped. Plenty of larger size lots and some level spaces to create homes on them with Edit Town And a better selection of males, George Dean is my favorite.
AP is even worse, there is no real park at all; at least one that I have found. No swing sets, chess tables and picnic tables on a set lot. Has plenty of nice size lots, and the families don't see to have as many problems as they do in SV. I haven't started to really look for a spouse for kids yet, though; so not sure of what I will find. I haven't found the saloon yet, probaly not recognizing it, won't look lik one from the old west. Same in males, I guess I want too much in the male selections.
Getting back with the question in the orginal post, the size of the lots are important, the unfiinished feel (which SV and AP seem to have for me), and a park large enough for the family to have something; play area, chess and a picnic table. Which RV and AP are lacking.
MF having the nice size of lots with homes on them or free to build on, a park and some nice males and females. Not the "goody two shoes" type, just not majority of evil, insane, mean type of males/females is important to me.