Sarisio: Final Fantasy VIII's Eden Summon was 3 times as long as Super Nova.
There's actually one rather significant difference:
In FF8, you can avoid seeing the Eden animation by simply not using that summon; it's not ideal, but at least you could avoid it. FF7's Supernova animation is the result of an enemy's action, and therefore, there's no way to avoid the animation short of killing the boss in question before the attack in question gets used (and, of course, said boss is likely immune to status ailments, so that probably won't work).
Also, actual timing (based on videos): Eden goes from 0:26 to 2:10 on one video, giving a time of 1:44 (1 minute 44 seconds, or 104 secionds. Supernova (US/International) goes from 0 to 2:02, so 2:02 (2 minutes 2 seconds, or 122 seconds), so no, Eden isn't 3 times as long as Super Nova; in fact, Super Nova is actually the longer of the two animations.
Edit: Japanese Super Nova (for those curious) starts (in a different video) at 1:28 and ends at 1:55 (wiping out the entire party in the video I chose). That's "only" 27 seconds (which is still way too long for an enemy's attack). I have no idea what possessed the developers of the US/International version to make the enemy's spell animation longer. Sure, it might look nice the *first* time you see it, but if the battle goes on long enough to see it a second time, or if your party gets wiped out on the first attempt, it becomes annoying and a waste of time.