Pulsefire Ezreal and DJ Sona are what ult skins should be.
Udyr however...
Udyr's ult skin should have been a remodel, his default look is old and terrible. (just look at his weird arms for example)
When you look at the Twitch remodel, Sion remodel, Trist remodel, Heimer remodel. Karthus remodel (Trundle was more of just a pointless lore change to recolor him and Sejuani was just to put clothes on her)
The quality difference from old to remodel is about the same as default Udyr and Spirit Guard Udyr as their new default skins. (Twitch, Sion and Heimer being the most noticeable)
Yet people had to pay $20-30 to get the quality on par with new champs/remodels.
Another big deal with the Spirit Guard Udyr was that he had new emotes and interactions, but these remodels/reworks also say different things when you buy different items too.

Pulsefire Ezreal completely changed his look with a new suit and everything, and PFE was the first awhile ago so it gets some slack in comparison to DJ Sona
I don't even play Udyr, I just think that DJ Sona makes Spirit Guard Udyr look so not worth the money in comparison.
After DJ Sona, the Spirit Guard Udyr skin should have been a rework, or a Legendary quality (1820 rp) skin at best. Dunkmaster Darius is more deserving of Ultimate status then Spirit Guard Udyr
Edit : the new Definitely not Udyr skin is a bigger character change then SGU, and its better looking.