At this point, I'd say defeating Jericho means very little to nothing. Fandango could have never defeated Jericho and he wouldn't really be any lesser of a star now than he is currently. Other than the commentators reminding us of it being the biggest upset in Wrestlemania history, no one really takes note of that victory. Ryback winning by roll up already means nothing, although Ryback has been booked to shit in general.
I think the first problem is that Jericho has never been a top tier talent on the same level of a Hogan or an Austin or a Cena (as proven by him never being booked as a consistent main eventer) and so you can't expect people to automatically think that defeating Jericho means the person looks like a much bigger star because of it. This isn't an insult on Jericho, just a bit of truth about his position on the totem pole in WWE in terms of his own star power. Just look at when he lost to Batista a couple of times cleanly back in 2004, for example. It was a good mid card victory for Batista, but nothing that made him into anything much bigger than he already was, and that was back then when Y2J was on the show full time. (Of course, if main event-caliber stars like Hogan/Austin/Cena were past their prime and only around periodically and spent most of their feuds jobbing, defeating them wouldn't mean a whole lot anymore either.)
The other problem that goes along with it is that Jericho is rarely booked into anything that feels important. If he won a championship and kept it for a while before dropping it, then yeah, that would feel like something. But him just bouncing from random feud to feud to feud where he jobs (Ziggler, Fandango, Ryback) does nothing much for any of the guys he loses to. It means more than beating someone like Heath Slater because of Jericho's past accolades and the fact that the announcers can remind people of them and no one really expects Slater to put up a good fight, but in terms of whether it's a huge career moment that really gives someone a rub in the sense that people see them as having more star power because of it, I don't think the two situations are really that different. A win over either Jericho or Slater means nothing in the long run at this point.