Hiya!
My 2¢ on 5e Saves is different than the above posters.

Saves in 5e are, as far as I read them, "when nothing else would come into play other than "sheer, uncut, dumb luck and godly favour".
I have found that Intelligence saves seem to have the most dramatic effect on the game. Dexterity tend to be "momentary", as does Constitution (even if "momentary" means..."until spell X can be cast"). Strength can be pretty dramatic as well, with failure sometimes utterly stymieing the PC(s) progress. Wisdom, from a sadistic DM perspective, are the most entertaining to watch (players role-play something they
really don't want to...e.g, being charmed by a hideous creature that needs them for a quick 'pro-creation' session, for example).
I also freely substitute various Skill checks in place of a Save if it's appropriate for the situation; e.g., an Athletics check for some particularly large PC race fighter guy trying to resist being "pushed back" (say, a Thunderous Smite spell). This seems to have worked out even better than flat-out "saves", IMHO.
One of the cool things about 5e is it's "lower baseline" (I think they call it "Bounded Accuracy") for numbers. It's really,
really hard to "build" a character that "wins" all the time in it's focused area. Well, unless you are using a bunch of optional crap like Feats and Multiclassing, and you have a DM who only tries to run games "by-the-book" (e.g., if the book doesn't say X, then the DM won't rule X, even though it makes perfect campaign-logic sense). If those factors are in play in your game...well, uh...prepare for a LOT of table arguments and DM frustration that ultimately leads to a dead campaign. The role of the DM as arbitrator of the rules is an actual requirement for the rules to run smoothly.
Bottom line: All Saves are equally useful, in my experience. Dexterity does come up a lot, but the effects are usually minor and/or easily overcome/rectified. Intelligence and Charisma ones are less common, but can have very dramatic and long-lasting effects. Constitution, Strength and Wisdom all come into play off and on, and can have vastly differing effects, overall. So...they are ALL equally useful. Don't sweat the small stuff. Enjoy playing your character the way you want, because 5e doesn't "punish" a player for taking "sub-optimal" choices...mainly because there are pretty much zero "sub-optimal" choices (unless, as I said, Feats + MC + bad DM are in play).
PS: I use "saves" when there is no skill that would be appropriate for a PC to use. For example, "Quick! We rush to that cobbler guy! The one we met in the inn who said he had a shop here!" ...DM:"Uh, what was his name and where did he say his shop was?" ... "Err...crap! What was his name?! C'mon guys...where was it? Weaver street or Water street?" ...DM: "Uh, no streets by that name here...you sure it was this city?" ... "Yeah...I think...double crap!" ...DM: "OK, Intelligence save time...".

This type of "save" comes up at least as often as a 'book requested' save, and when these one's come up, it can be anything, but typically Intelligence, Wisdom and Charisma in my game...but only by a smidge.
^_^
Paul L. Ming