A True RPG uses stats-based combat, and player skill is represented only by strategy in selecting orders.
A True RPG gives you choices in where to go next. Corollary: the tutorial phase of the game is only over when you can meaningfully choose where to go next.
A True RPG rewards curiosity and exploration; some of the game's finest treasures will be had by finding something secret.
A True RPG has a compelling story; you should want to finish the game in the same way you want to see the end of a movie.
There are more (I've got opinions), but these are the interesting ones for the purposes of this writeup. These are some of the ways I'd have insisted that FFVIII shines.... but on my last playthrough, I realized that the game actually fails to deliver on all counts.
I've often derided FFX for being an "RPG on Rails" - until the very end of the game, your path is literally one-dimensional; you can go forwards or backwards. Same with FFXIII. I couldn't shake the feeling that "tutorial mode" persisted right up to the end of the fourth disc. But FFVIII does the same thing - you don't actually get a choice of where to go next until the middle of disc 2, and once you *are* given that choice, you really only have two options: sidequest city that you have NO REASON TO KNOW EXISTS, and next plot point. You can also find a Chocobo Forest, which doesn't help you because by the time you get there you have land transportation covered.
Rewarding exploration? Not so much. You can find magic draw points, but your magic caps out pretty quick. Or, you can get cards, which refine into items, which refine into magic. There are a couple of Guardian Forces you can find in the wild, but they're either obvious or they're so hidden as to nearly be easter eggs; they don't reward exploration nearly as much as they reward buying the official strategy guide (which was the thing you did Back Then™).
As far as the story goes, it's obviously a subjective call. All I can really say is that if your story hinges around a high school that teaches its students to fight with personally styled weapons, the heroes all have amnesia and the villainess is a time traveller, then you'll have an easier time impressing 19-year-old Mark than 33-year-old Mark.
Ultimately, I think I was really playing the game I expected it to be, and not the game as it actually was - like, I believed that I could explore, so I didn't notice I couldn't. I'll be interested to see how Skyrim holds up for me in 15 years. Has anybody else here experienced this kind of thing? I'm curious how common this actually is.