They all svcked.
The effects really need a revamp. The majority of effects in Oblivion were clouds of dense smoke/light with different colors, such as healing spells being a cloud of bluish white light, and illusion spells being a cloud of greenish white light. A lot of the effect sounds were also that damn annoying sparkle noise.
As for Morrowing, the majority of effects were that weird double sided line of light that first flew out from your body, then back into it, and the effects just changed the color of that (purple for alteration, green for illusion, etc), and a lot of them had either that really loud swirling "sssweeesssww" noise (like for restoration) or that wobbling low "wbbblllll" noise (for alteration or illusion).
I'd definitely appreciate better effects if we could get them, but I'd rather we get better SPELLS.
I have to agree completely on this. The spell graphics from the Elder Scrolls series have always been rather underwhelming, it's one of the reasons why I really don't think the games do magic justice. I'd like to see something a little more impressive, more importantly though, I want actual VARIETY in spell effects. As of now, while we get differences between on touch, on target, and on self spells, there's little variety beyond that, sure, different spell effects might look slightly different, but they really feel like they just took the same effect and slightly changed the overall look of the particles involved, well I suppose that at least in Oblivion, destruction magic had you shooting a ball of fire, a bolt of lightning, or a big cloud of frozen air, but beyond that, the effects all felt far too generic. If you play some other fantasy RPGs, you'll notice that there can be a fair variety both in how spells look and how they behave, we get none of that in the Elder Scrolls. In part, I think the culprit may be custom spells, in order to make it easy to create new spells, Bethesda made the spells themselves fairly simple, resulting in better spells really feeling like pretty much the same spell, just with different stats, this also makes creating your own spells not very satisfying as you can't create a spell that will actually feel unique. Honestly, if it would give Bethesda more freedom to get creative with spell effects, I'd be pleased if custom spells dissappeared from the series forever.