I dunno... I kinda hold the opinion that modern console rpgs should have at least 40-100 hours of gameplay with the NIS published games (srpgs not included) being the exception since they're fun and feel just the right length even if the over-all playtime is short. (Final Fantasy X and XII, Persona 3, and yeah, even FFVIII and both VP games had at least 40 hours of gameplay, I think) Tales of Phantasia, which was released at about the same time as SO1 had 40 hours or more of gameplay.
What I mean is more and more RPGs nowadays is shorter than they're used to be. 20+/25+ hours RPGs is quite common nowadays (please don't count the side-quest, 100% perfect completion, additional 100 floors sanity-hazard dungeons, and NIS TRPGs eg:Disgaea
). Perhaps now they aim more to short but fun and challenging gameplay (and graphics) that also intended for busy people.
I often get frustated finishing 40+ hour RPGs, only to know that there is more than one ending and there is no "New Game +" around.
Of course long RPGs are still around. FFXII, WA5, and bunch others (although there are less and less RPGs for PS2, bohohoho...)
BTW, SO1 got out after ToP (since most of the crew are the same people, hence producing similar games). Same case with Tactics Ogre and FFT. But, yeah, perhaps ToP is long (despite being earlier) although I don't know the exact hour. I didn't notice it before, it seems short for me.
Note: Perhaps the reason of it being so short is the hardware limitation? 40+ Megs in a single cartridge is incredible, not to mention the amount of voices. I still remember the first time I hear the ToP opening song, I literally cry (of bliss and happiness). I also scream when I hear Cless shout "Koga-hazan" in ToP.