I think all of the towns are a great place to do an immortal dynasty. I've played in them all. My current one is in Lunar Lakes. It all depends on what you want in a spouse. My advice would be to use the Sims Wiki and figure out which town you like the best. There are some towns that have advantages over others but really I suggest doing it in a town you are familiar with so that you always know where the special seeds are and the best fishing spots to help with that first generation.
Do some research and just goes with what your gut says is right. That's basically the only advice I can give you. Your taste in Sim men may very likely vary from my taste in them. You can look up Single Sims on the Wiki and get the list of all the single ones to peruse and choose from.
