Hiya,
Probably don't need my take on the game, but...
After revisiting FF3 (one of my favorites) and Chrono Trigger (absolute favorite), I think I'd stick Phantasy Star 4 right in between there. There are lots of things I'd like to talk about, but I'll keep it sorta short (I have less than 10 posts but most of them are LONGGG. -.-)
What's good about Phantasy Star 4 and why you should get it:
-Originally retailed at $90, before dropping to $30. Higher than Chrono Trigger's $80...
-Best character development for any 16-bit game (and probably 90% of all RPGs).
-Has a "Talk" function that makes your characters talk to each other. Why? So you NEVER forget what your next objective is. So if you stop playing for months then come back, you can pick up where you left off.
-Awesome music.
-Great cutscenes, anime-style pictures.
-Excellent dialogue. None of it seems forced.
-Not a happy happy RPG (ie, Mario RPG). Enjoyable for many age groups.
-15 different combination attacks are possible using 'Techniques' (magic is defined as something different in this game). You get no hints or leads on how to do these... but they can be very strong if you happen to stumble across one.
-Graphics are cool.
-Vehicles (notice it's plural).
-ALWAYS has a good reason why you can't have more than 5 in your party at once.
-Battles kept short, quick, and to the point. You'll realize this after your first battle. If it's a longer battle, it's probably because you're thinking about how to survive.
-Really really cool storyline.
-Bosses can be pretty hard. Seriously.
-Great humor.
-Macros can be set in and out of battle, to shorten fights. In other words, your characters can have set commands if you don't feel like always inputting them each battle. Very useful, even if it's just the "everybody fight" macro.
-Satisfying ending.
-Memorable.
Is that enough for you?

Some of them seemed like I was stretching for ideas... but those were just what jumped to mind.
As for Phantasy Star being rereleased, there was Phantasy Star Collection for GBA, yes... but that only included PS 1-3, whereas the Saturn version of Phantasy Star Collection (pre-GBA) had PS 1-4 as well as the television commercials for them, and so on. This is the only other time Phantasy Star IV has been on another console. Hopefully, though, it will show up for Playstation 2, as they are remaking and rereleasing Phantasy Star I with new graphics, etc... in Japan.
For everything Phantasy Star, try:
http://www.phantasy-star.net/
It's awesome. It really is.
And yeah, the Dreamcast Sega Smash Pack only has Phantasy Star II and Shining Force...
...don't get me started on Phantasy Star II.

Simply put, it's another great game, but Phantasy Star IV is more 'user friendly' I guess you could say. ...well, let's put it this way. Phantasy Star II (in the states, at least) came packaged with a strategy guide that mapped every dungeon, and was basically a full walkthrough.
~Kap