Myst 3: Exile was the last Myst I played. It was pretty decent story and character wise, and even has multiple endings.
From what I hear and read, the ones after that were dumbed down with hint system and such.
IV is fucking TERRIBLE, just watch a LP video. It is basically add a bunch of shitty puzzles together because that is what Myst is about, instead of the organic integrated puzzles in the first 3. V was actually... OK. And was done by Cyan (and the first time they used an in game NPC charcter model instead of a "cut scene" NPC).... which was odd (probably due to the low budget).
Pretty much I - II - III are the best of the series.
The Myst games are some of my favourites.
I: Myst is a decent, short game; but it has its problems. Some puzzles are just to awkward to interact with: even if you know what to do, it can be hard to get the answer just right. realMyst might be a better alternative, but I haven't played it in a while so I'm not 100% on how it compares to the original. If you're deaf you'll probably have quite a bit of trouble with this game (there's at least one puzzle off the top of my head that would require a walk-through if you are).
II: Riven's one of the best adventure games I've played; I've never been as satisfied when things have clicked into place as they did in this game. The one major annoyance has disappeared now you can get the game online or on one DVD (vs the five CDs it came on originally, and required you to switch if you traveled quite regularly). Some of the puzzles are arbitrary, but they still somehow seem appropriate. It's definitely the best game of the franchise. There's also an Easter egg (I believe, it may be a separate video) where the villain sings opera.
III: Exile's a great deal of fun, but it's rather easy, and one of the worlds can be hard to navigate if you don't know where to go, especially with the new 360 degree range of vision. But the others have very nice "payoffs" when you complete them. Also Brad Dourif.
IV: Revelations, well, I kind of like one of the ages, and the new in-game camera makes things a fair bit easier note-taking wise (particularly helpful in this type of game), but I really remember very little about this game, like it fell into some black hole. Some of the designs are just ass-backwards, and you have to babysit a little girl. Jaesun's not wrong: it's the weakest entry of the franchise, aside from perhaps...
V: End of Ages. But dear lord did I HATE this one. Yeesha consistently doesn't talk like a normal person: I guess after the events of Revelations she got heavily into the pot and became intolerable. The main villain is basically Lyric Suite, only you can't ignore him. And you have to use a tablet to draw pictures: a nice idea, but it can be as finicky as hell and just becomes tedious once you've "solved" the puzzle to draw it on correctly. Some of the puzzles were neat, I guess; the problem was the story. And maybe the fact they'd switched to using animated figures instead of actual actors. I like this one the least, because I fucking loathed it.
?: Uru; the single-player MMO. This and its expansions are a GIGANTIC game, and well worth the price. It's a far better game than the last two. However, there are some really, really badly-designed puzzles (I think in one of the expansion packs) where you have to wait in real-time... and can fuck it up so you have to do it again. I think you can still play the MMO side, which I haven't done, but I've seen a good LP of it and it does some pretty good things with it.