You shouldn’t bother with the NES versions of the first three games. There are several packagings of Dragon Quest 1&2 (the first seven games of course were known as Dragon Warrior in the US because the Dragon Quest trademark was taken) and the newer the reissue, probably the most qol improvements it has. They’re very grindy in the originals and with bugs; your answer to how long they take is, longer than it’s worth. Dragon Quest 3 HD-2D just came out and I plan on buying it soon, Christmas at the latest. It’s getting fantastic reviews and actually is more a reimagining of DQ3 rather than a straight remake. They’ll be doing these remakes of the first two games later. I can’t wait for DQ4-6. Five and six were never released in America and there were no fan translations when I lost interest in video games. Number four is much different, much more ambitious, at the scale of Final Fantasy, but it’s only a tantalizing glimpse on NES.

One of my favorite capsule summaries is GOG’s of Doom. It’s very concise:

You’re a Marine, one of Earth’s best. When an experiment malfunctions and opens a portal to Hell, the base is overrun by bloodthirsty demons. You must shoot your way out to survive.

Note that, like in a lot of “Satanic” media, the spawn of Hell are the bad guys you’re trying to kill, you’re literally opposing Satan. (An occasional comma splice for effect is acceptable.)

I don’t think I need to add that I wasn’t allowed to play Dungeons and Dragons.