My brother owns a Sega collection-style game for the 360, and I played about 10 hours through Phantasy Star IV. Sadly I moved out before I had a chance to complete it, and keep meaning to come back to it one day. I could buy my own copy of the collection, so that I could play other classic Sega games, but I'm not in a position to splash out a lot of money on a collection of games, many of which won't get played at all. Is it available on the Wii U/3DS eShop? Both of those would be ideal, since I could play while doing other things (like working through my massive backlog of TV shows and films).
It's available on the Wii Virtual Console store if you have that, I have no idea about thee Wii U. It's also on 360/PS3 on the Sonic's Ultimate Genesis Collection.
You can see if you can get the game cheap on ebay or amazon that is probably your best bet if you don't want to save some money.
It's pretty much available on anything modern these days. Steam/PS3/3DS/Wii U/Wii. Sega has pretty much made themselves available on every single platform except for GOG. Pretty easy now.
Phantasy Star IV was my first RPG. If you like it, I recommend playing Phantasy Star II and Phantasy Star, but keep in mind they're a lot harder. Phantasy Star III is a little weird. It's really cheap on Steam and if you buy the bundle, you can get II and III.
I would highly advise you to obtain the ROM from somewhere, and emulate it on your PC/laptop. It's really easy to figure out, and it's legal if you already own the game. Also, the other versions are also emulators, but masked, so it's just cutting out the middleman and doing it yourself.