In my opinion, any route that connected the Jersey Shore with the Philadelphia area would make sense. Specifically, if Bayhead to Seaside Heights to Toms River to Camden/Philadelphia would make sense - especially in the summertime's.
It would also be nice to see Cape May, Ocean City, and Wildwood still having service, but I don't see those lines being profitable outside of the summer months. They could've been great railcar storage in the winter months though.
I think the severed route of the old C&A between Bordentown and Jamesburg would make sense as well, since it parallels the Northeast Corridor, and would be an excellent route to re-route freight trains off the NEC going to Philadelphia. You could also use it as an "overflow" route for NJT trains during rush hour/times when the NEC is crowded.
I think the old Bel-Del route would make an excellent extension for the RiverLINE NJT line as well. The areas around the old Bel-Del route have become pretty gentrified touristy areas, and some consistent public transit up there would be very beneficial. It's also been said that if the Poughkeepsie Rail Bridge didn't burn/was restored for rail service, the Bel-Del would likely still be in use for freight service.
I think a lot of us here would like to see Lakewood - Winslow Junction back in service again, but that likely won't happen. That being said, that route would likely still be a very active freight route if the Pinelands Commission didn't come around. There were a lot of sand pits in the Pinelands, but the Pinelands Commission does not allow for any (new) development in the Pinelands, so that meant when a lot of sandpits that got regular service dried up by 90s, there were no options to open new sandpits.