it's the vanilla-ness of the characters. it was too much of a VII-clone, but it didn't have some things that made VII wonderful:
1.) most of VIII's main characters were really just vanilla and were cheap knockoffs of VII counterparts:
squall = cloud with even less personality. he acts like a pissed off guy who thinks he cant help anyone just like cloud, but he doesn't have a reason to do it except being 'him'. the gunblade was another cheap imitation of the much more iconic buster sword. His costume is absolutely ridiculous and so obviously detailed to make it look 'special'. even his limit breaks are obvious cloud impersonations (he had a blade beam, omnislash and others)
rinoa = tifa/aeris rolled into one (since she's the only love interest) with neither the personality nor the complications of a love triangle. what made VII's love story intriguing is the fact that there were two people fighting for cloud, and hence there was uncertainty and a lot of 'what ifs'. aside from that, tifa and aeris represented very strong personalities that were very different from each other (tifa = strong willed, direct, and up close, aeris = the damsel in distress type). rinoa was only like an ordinary girl and had no uniqueness about her.
seifer = a weak ass sephiroth. VII's rivalry of cloud vs. sephiroth was intriguing. VIII's rivalry of squall vs. seifer was not only prematurely ended, but also insignificant. squall's rival never really got enough screentime to be memorable.
selphie = obvious imitation of yuffie, but had a lot less bitchiness. this character type is supposed to be all over the place and annoying as possible, yet cute and likeable at the same time. unfortunately, selphie never got to express that in the same way yuffie did because she just didn't have enough personality.
the guardian forces = the same old thing again. ifrit, shiva, bahamut, odin, and the old dudes are back.. again.. there are no real new powerhouse summons that one could identify VIII with, except if you count the almost-impossible-to-get Eden. aside from that, the animations were extremely long and exaggerated just to do... 1k damage. ifrit hurling his big red fireball looks like its going to destroy the world, but it only deals less damage than squall's normal attack. wtf?
omega weapon = back again, and this time much weaker and less iconic. he's smaller, and with the ability to use hero drinks and auras, the fight is mathematic. unlike VII's weapons, that required a whole lot more effort and work to beat (remember what you needed to do to beat emerald weapon? omfg). to beat omega weapon, all you need is to... play card games and acquire the gilgamesh card. 10 holy war drinks = your entire party is invulnerable for the entire fight. blech.
2.) main enemy confusion. we weren't really sure who was the main bad dude till the last few hours of the game. therefore, no real motivation to beat the game:
seifer = as mentioned, the rivalry never really blossomed to anything
edea = for a long time, she was the 'destroyer of the world' that we needed to defeat. built up animosity after all that time disappeared.
ultimecia = an unknown quantity without any backstory given. didn't really care about defeating this woman.
3.) junction, GF boosts, lack of armor, aura, hero drinks, etc. made things far too mathematical and calculable.
everything relied on numbers, and everything relied on your ability to calculate. this meant that little was left to the imagination, as everything is already laid bare, as to how much damage your attack or GF would do.
the bad thing about this is that there's no mystery anymore. after tapping square for 200 times while ifrit hurled his huge red fireball at someone, you already expect a certain amount of damage, and the thing becomes routine. as opposed to VII's system, where critical hits and random damage increases are common (knights of the round damage is really spread out there), you get a feeling of 'whoa' when a particularly huge hit comes in.
aside from that, equipping certain magic effects to stats (like curaga to HP) already shows you exactly how much you'll have, and all you gotta do is allocate the best one for each particular stat. no balancing is needed. there was no sacrifice necessary for certain stats to get others. in VII, if you wanted more attack power, you would have to sacrifice your magic power. in VIII, if you want both, you can just junction the specific magic types to both stats and get them both. it leads to a lack of feeling of necessity and lesser customization, as you can just max out everything.
the lack of armor effects also removed more elements of mystery and player input. in VII, armor effects were really important for specific battles (magic def vs. physical def vs. pure HP). in VIII, for example, you can put up as much HP as you want without sacrificing defense in any way.
the aura that made you able to limit break as much as you want made the concept of limit break something 'normal'. a limit break is supposed to be a 'limit', meaning 'uncommon'. but again, VIII made you able to calculate when you wanted to do your special attack. there's no randomness or anything to look forward to.
the hero drinks made you completely invulnerable to anything. needless to say, it made you able to defeat anything and everything without catching your breath. no randomness, no fear of defeat. everything is simply calculable.
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so in the end, these three reasons gave way to a bit of hate on VIII, because it was lacking in the things that made VII immortal.
but it did have that crazy great card game. i loved that.
