... I've tried to play several of the older ones. Some I made an hour or two in, some not. The side scrolling one I really wanted to get in to, I spent a couple hours and never made it more than two or three screens in. The combat system (I.e. what you spent 90+% of the time doing) back then (for all of them, and especially the side scroller) was honestly just kinda' miserable to play. Almost like a top down Joust, except more fiddly and significantly less enjoyable. Can't speak much for the newer ones, though. Hear they abandoned what was imo one of the worst incarnations of top-down combat the world has ever seen, at some point, but the early Ys soured me pretty hard to the series, for all I've got a fair amount of respect for it vis a vis the influence and popularity.
My best recommendation (short of indulging in emulation, anyway) would be to see which in particular is enticing you, and then hunt down a video or two from a let's play, see if the gameplay in action is something that appeals to you. So far as the older ones and their remakes are concerned, though, I'd honestly just suggest watching/reading a LP and saving yourself the trouble. Good to see some gameplay or ride along for a playthrough or two just 'cause of their place in gaming history, but to actually play it... there's a lot of significantly more enjoyable things you can do with your gaming time.