Tshober: OP, 30 hours is nowhere near enough to finish an old school RPG. 60-80 hours was par for the course for the lighter ones. I know that I missed a TON of quests back in the day, so I hope to complete them on this run-through.
That might be true on your first attempt at the game, but quite a few of them can be beaten in under an hour, sometimes even under 10 minutes. Speedruns of many old school WRPGs (and it really is generally WRPGs, not JRPGs, that are this short when speedrun) are really that fast. The wide-open worlds make it so that, if you know exactly where you need to go and what you need to do, the game can be beaten very quickly. Also, there's the whole issue of what is required and what isn't.
For example:
In MM2, there's a major quest that only provides a piece of information needed to beat the game. If you happen to already know it (for example, you looked it up online, or you already know from a previous playthrough), you can skip that entire quest. Also, choosing your party carefully can also reduce the number of quests you need to do, and there is a feasible way to raise your character's level into the 20s quickly.
The Ultima games can be mostly beaten somewhere on the order of a half hour, due to the lack of need to learn things like the mantras and knowing exactly where things are. Ultima 4 is actually an outlier, taking over 2 hours to speedrun, because of the need to increase your virtues.
Morrowind, despite being a huge game, can be beaten in less than 4 minutes. Even the "all main quests" category takes only around a half hour.
By contrast, the original Final Fantasy takes over 3 hours to speedrun (assuming that arbitrary code execution is not used), and that's if you're lucky. Thing is, you actually have to do most of the tasks in the game, and you need to be a high enough level to defeat the bosses that you encounter. (That's one other notable difference; early WRPGs don't always have final bosses, but JRPGs always (or nearly always; can't think of any counter-examples at the moment) do.)
Waltorious: I recently replayed the first Finfal Fantasy game, and it was really interesting to compare it to MM1. They came out close to the same time (at least Final Fantasy did in Japan; it was several years later before it came to the US) and the difference in technology was impressive. Final Fantasy is much more colorful and has full music, compared to the barebones MM1. It was also interesting to see the influences of early computer RPGs on the first Final Fantasy, which is a far cry from the direction the series eventually took.
You might also want to try playing the original Dragon Warrior. It is another game where you can see the influence of early WRPGs, and it's actually quite different from most JRPGs. Consider the game's dark dungeons (you need a torch or spell) and the need for keys, as well as the fact that the game is open-world, with your exploration only limited by your ability to survive encounters.
I could also recommend Final Fantasy 2 (Famicom, not SNES) as another interesting game to play; it's somehow both open world and linear. You can reach most of the towns right away, but you can't actually do much there until you progress the story. It also has, shall I say, some bizarre balance properties; for example, heavy armor is worse than useless. (Also, there's the non-traditional "learn by doing" growth system, which is an interesting idea, but maybe not the most well executed.)
There's also the original Phantasy Star on the Sega Master System, which even has first person dungeons. (How come Phantasy Star got them while the SMS version of Ultima 4 did not?)