The senators alternate may be among the top jerseys in the league period. They'd be absolutely foolish to not make it their permanent look, with a corresponding white version.
Besides that, I really like the flames retro alternate, which I also believe should be their full time jersey, and I was a big fan of vancouvers white alternate, with the V in the stripes on the sleeve. Not sure if its still being used though. LAs purple and gold alternate is really cool too.
A summary of my criteria for a good jersey is-
Logo: Strong relatively simple image with impact and strong dynamic outline. No bad illustration skills, no collections of itsy bitsy lettering and tiny clip art images all montaged together. Logo is usually best if it is not block lettering only.
Looking at a webpage that displays all of them, my favorites are:
1. San Jose
2. Calgary (ew, Calgary)
Those are the only good ones IMO.
The Rangers and Bruins jerseys have some appeal because of their simplicity and classic look, but some slight sticking points exist that keep them off my list.