Again, keep in mind that for that era of the PS1, those graphics were incredible. The pre-rendered backgrounds may look a little cheap, but stylistically they were a good idea as they looked better than full 3D mapping would have allowed, and freed up some space to further improve the battlers and the like.
The in-battle graphics are fairly close to the pinnacle of what was achieved in the PS1 FF games. I can see no real improvement (or room for improvement, for that matter) between number seven and number nine, although it's true that number nine did make its characters that detailed in and out of battle. But give Square a break here, FFVII was their first foray into the third dimension. Up to that point, all but the most recent Final Fantasies had small sprites for the overworld and slightly more detailed ones in battle. Since they were testing out the boundaries of the technology at this point, I assume they chose to stick to the undetailed overworld character models and focussed instead on the advanced battle models.
As for your second point, I revive one of my earlier points: You gotta ask yourself, were most of those cliches before Final Fantasy VII? Spiky-haired heroes and bishies were well-established standbys in anime by this point, but I think FFVII is one of their earliest forays into video games.
Besides, even if these cliches were considered such before FFVII defined them, a few of your descriptions strain my belief a little.
For starters, the "dark vampire man" can transform into hideous uncontrollable monsters. I think that makes up for any infringements he might have made with his pimpin' cape and gauntlets.
Jet pilots are cliche, too? What? I guess if Cid were a train conductor, he'd be more original, right?
And Cait Sith... Come ON, man! He's an animated doll that happens to betray you! Betrayal itself isn't a cliche, it's a literary tool! I think the whole doll thing makes up for everything else, really.
The way I see it, for the most part the very reason we see these characters as cliche is because after FFVII's rousing success, people got sick of every twelve-year-old writer wannabe copypasting the plot or characters or both into their own personal fantasies. We can't look back on then using the strictest standards of now, because I'm pretty sure the game changed things around a lot in its heyday. It's like going back to the days of Shakespeare and telling him that Hamlet's premise is overdone by today's standards... Okay, it's not so strong as that, but you see my point. XD
And come on, tell me you didn't have fun playing it for the first time. :\