Yeah FF2 Dawn of Souls was a pretty swell game. I think I played it back in 2004 or so. The FF2 postgame was great because it brought back all the playable characters who died during the story (with the same stats they'd had when they died) and that was your group. Then they go through Hell and fight the final boss down there where he's of course even stronger than the one the main party fights during the story.
FF1 Dawn of Souls was even better because instead of one big postgame dungeon, it had four new dungeons spread throughout the game and some of them could be done midway through the main story. I think two were postgame-difficulty, one was lategame, one was midgame. Something like that. You could get really good gear in these places so in a way they could trivialize the main game. Most importantly the dungeons were really inspired and brought back a bunch of boss fights from FF3 through 6. Each dungeon represented a different game.
I played all of the DQs and PSes. Didn't beat all of them but I played them. Phantasy Star 4 is a pretty incredible game and I don't think enough people know about it. Rarely seems to come up in RPG discussion much less in the same boat as FF and DQ. I consider PS to be the third of the "big 3" RPG series of the 80's and 90's but it's easily the most unsung.
Majority of all three series are good, but the worst games get very bad. You couldn't pay me to play FF2 NES and Phantasy Star 3 back to back. DQ7 isn't as bad as those, it's just super long and mediocre.