I can kinda understand people liking Online over the Classics.
As much as they got good stories they require a lot of energy and perseverance.
Phantasy Star I without a proper GameFaqs map (or drawing them yourself) is harder to do. The Sega Ages 2500 series version on the PS2 called Phantasy Star Generations was a pretty good remake mechanically but at the cost of having a "cheap" looking game with a 2D art style that doesn't have the charm of the original nor the quality of the Online nor Universe games it's harder to get into. The Switch version of the Sega Ages release added an automap (which fills as you advance) and an easier mode for people who don't want to grind but sadly it's digital only on the Switch.
At best you can try the SMS Power romhack that vastly improves the game while having a more faithful script but once again it doesn't have an automap. I'd love to see the best of both worlds.
As for Phantasy Star II the story is much better but alas, the dungeon and battles are a hassle to do because of the slowness of characters that aren't on the center of the screen (so this makes bad visibility) and the flashing that are an eyesore. The Genesis Mini II release apparently fixed many issues (as well as the Phantasy Star Collection version on the Saturn with fast running yet is only in Japanese).
Phantasy Star III is the black sheep for a good reason and we needed more save files for each generations to get to see each endings so you'd need savestates specifically for them.
Phantasy Star IV is on the other hand perfect (despite the grinding) but that's because it was the end of the series.
Online may have a clunky battle system (with combos to keep) and the lack of Photon Arts make it stiff yet I still prefer it over spamming PAs which is sadly what HL becomes in PSU and PSO2...
I still think that Portable 2 (Infinity) has made my opinion of Universe much better. PS Zero could've been a better PSO if the DS had a proper stick and had a ZL/ZR.
I need to get into PSO2's first trilogy of episodes which was a solid story before they changed director for Episode 4.
That franchise had a see-saw kind of release, both good (if not really good) and mediocre releases...