I am also noticing what attracts me, and one of the first items to me is whether the sim holds together or not, that is, is there an overall theme, and is there something original too in that theme? An overall theme pretty much eliminates most mainland sims. There, if I find anything of interest, it would be a hidden gem lost among the rest of the plots.
Sims or group of sims that are used for rp (role-playing) tend to have an overall theme. So did this sim that I came across yesterday, Casa, a gorean rp sim. There was no-one around when I visited it, and it was lucky because I could not find a visitor tag.
The build was average with a few interesting ideas, like this prison on an island.
There were a few buildings often with rp stores at the bottom and living quarters above.
A communal bath.
Some kind of watch tower.
The fortified city did not make much sense to me, but I don't rp there, and know extremely little about Gor. You could not set watches on the walls... might as well have no walls, then.
Houses on stilts, warehouses completed the picture.
It fits a medieval, pre-technology society, living off trade, though what they traded was not clear from this visit. However, the sim itself was some kind of story book, if you want. The builds themselves were more interesting than the landscaping.