Kuja`s, I honestly hope you have more tactics than some lazy, half-assed "He'll breathe fire balls if he does that, and 3 if he does that, and another when he tries that! So hah!" Once Sephiroth realizes that Bowser is only going to jump and spit fire, other tactics would surely come to mind.

Not all of Seph's magic spells take this long, drawn out process to cast as you are speculating, only Meteor really does. Just because in game cinematics are used when a spell is casted, doesn't mean that is how long it is taking for the spell to be cast. If you notice, no one's attack meter goes up during these times, which means that instead of just having this spell hit, they are slowing down the whole process and showing the player the origins of how the spell is working, which is aesthetically pleasing for gamers.

I'm sure it is the same for Lightning spells; If they really wanted, they could probably show clouds whirling above in the sky, and the energy of actual lightning being drawn into the hands of the caster, but we already that something like that is probably happening, so why bother slow the game down that much. However, with spells like Holy, Flare, Ultima, etc. not everyone is going to know what the fuck they really are, so a little introduction to them is necessary. If you notice, there are many spells in the game that have a long cinematic when it is first shown in the game, then a significantly shortened synapse thereafter.

Sorry for the long speel, I'm just trying to show that Seph's magic would certainly be a factor, just not every spell. And it would certainly be just as affective, if not more than any lame ass fire ball Bowser would pansily spit at Seph..