2 > 1 > 4 > 3
If you are interested in playing 1 and 2 you are gonna need to play with a speedup option,else the grind is unbearable.
But i guess that applies to most old school jrpg.
If you though the second was was grindy,well the first one takes that title with ease.Here are my two cents.
Background: PSIII was one of the first 16-bit jRPGs I played, so I have a soft spot for it. Given the lavish praise PSII received, I went back and tried many times to play it. Later, I played PSIV. I've never played PSI.
One of the cool thinks about the series is that, like Might & Magic, the games all take place in the same universe and interconnect in various ways. (Less so than with Ultima.) PSIII is the most separated from the others, but they're all a coherent whole with specific plot points, themes, mythology, and visuals arching over the whole series. I imagine that if one played the series start to finish, it would have been a particularly special experience -- each game was a significant technological and narrative achievement at its time, so in "real time," the bright spots would've burned brighter and the dark swaths would've been much harder to detect. For instance, while PSIII gets a lot of hate, I really enjoyed it at the time.
As others have said, PSIV is the best by a country mile. It has a cool use of manga cutscenes, the characters are the best developed (within the real of anime cheese), the visuals are the best overall (though each game has aspects that outshine the others), the music is catchy, and the battle system is complicated and clever. There's a neat bounty hunting mechanic, IIRC, which adds a gameplay layer that makes the grinding less annoying.
PSII's grinding and encounter rate is appalling. I could never finish it as a kid. Even played on an emulator with quicksave and speed-up functions, I'm not sure I ever made it all the way through. The aspect of the game that is most praised is its use of characters and plot twists; in 1989, these were groundbreaking simply because jRPGs had such thin plots and characterization. 28 years later, they are worn out cliches and very thin and unconvincing in comparison to even games around the same era. The combat system is attractive, but boring. The large roster of companions, whom you can freely swap in and out of the party, is a neat concept but ultimately tedious because inactive characters don't level, grinding takes forever, and to swap characters you have to schlep back and forth to your home.
PSIII has several cool ideas -- it spans three generations, and at the end of the first and second generation you pick which of two brides to marry, meaning that there are four paths through the game. While there is considerable overlap in content, there are also some unique elements to each such that if you play them all, you learn more about the overall plot and characters. There are some nice touches like characters who are young men in one generation showing up as old men in the next. The general magic vs. tech theme is pretty lame, but when I played it it seemed novel enough. It has a quasi-Metroidvania exploration system (not uncommon to jRPGs of the era) where you see areas but can't get to them until you have some new vehicle or power later. Overall it's not a great game though.
I think my bottom line would be that you should just play PSIV and skip the rest, unless you have huge helpings of time and a high patience threshold, in which case the experience of playing all four will probably be marginally better.
PSIII has several cool ideas -- it spans three generations, and at the end of the first and second generation you pick which of two brides to marry, meaning that there are four paths through the game. While there is considerable overlap in content, there are also some unique elements to each such that if you play them all, you learn more about the overall plot and characters. There are some nice touches like characters who are young men in one generation showing up as old men in the next. The general magic vs. tech theme is pretty lame, but when I played it it seemed novel enough. It has a quasi-Metroidvania exploration system (not uncommon to jRPGs of the era) where you see areas but can't get to them until you have some new vehicle or power later. Overall it's not a great game though.
I think my bottom line would be that you should just play PSIV and skip the rest, unless you have huge helpings of time and a high patience threshold, in which case the experience of playing all four will probably be marginally better.
It's worth mentioning that all the games have modded versions which make combat more interesting/ difficult (since that's a general "weakness" of the series). So if you aren't hung up on playing through the "original" experience, you might enjoy a mod more (especially PS III).
http://www.pscave.com/
There are also the remakes of Phantasy Star 1 and 2 to consider. I never played them, but I'd assume they would remove the grindy nature of the games, right?
A lot of old JRPGs that are considered to be grindfests really aren't (examples: Final Fantasy 1-3, Dragon Quest 2, Mother). The key is to make use of items and spells all the time, to run from battles that are not worth it (enemies that give debilitating status effects but very little reward), and to retreat back to town when you are in over your head.
Maybe, but I'm not persuaded. To some degree it depends what you mean by "grind" -- if you mean walking in a circle leveling up in order to advance I still think this is a major part of those games. But I think what many people mean is just the endless churn of random battles against low-difficulty enemies that operate as a slow attrition of short-term resources balanced against a slow addition of long-term power. You may be right that the battles are less miserable and marginally more tactical if you use your spells and items (though IIRC, many of these games had nothing other than healing items), but that is certainly how I remember playing them at the time -- particularly Dragon Warrior and FFI. It wasn't really until the 16-bit era that it made sense to stockpile spells for bosses because the 8-bit era didn't really have as many bosses. To me, the problem was that the battles were too frequent and too boring. Thus, for instance, the idea of playing Phantasy Star for 12 hours on a speedrun or 18 hours in normal gameplay is hardly appealing...I think RPG speed runs have proven that most RPGs aren't grindy. We were just playing them wrong back in the day.