Alduin appears to have been the only dragon that can resurrect others, as this explains their absence while he was displaced in time. However, after his final defeat, dragons re-spawn in the game.

Does this imply that the Thu'um he used to do so is now more widely known, and other dragons (Paarthurnax, for example) are using it?

I think the implication is that he just raised a lot of dragons off-screen. The ones that re-spawn at dragon lairs are just bugs. Also, once a dragonborn kills a dragon and absorbs its soul, that dragon is gone for good.

Also, I think the devs wanted the player to have a way to get more dragon souls after the main quest. I'm sure some people never finished Oblivion's main quest just so they could collect a ton of sigil stones.

Well, only dragons can absorb each other's souls, so maybe they all can resurrect a dead dragon that still has its soul, they just never wanted to?

I suppose it's not impossible for another dragon to learn the shout he used, and it would work as long as the target dragon still had its soul stuck inside its skeleton, and not inside the stomach of another dragon.

The words of the shout, Slen Tiid Vo, translate to Flesh Time (Opposite of), and the Dragonborn learns Slen and Tiid as part of other shouts. I imagine it would be difficult for a mortal to understand the meaning of the "opposite of time" though, which I suppose might be like the untimes of the Dawn, as mortals can only perceive linear time properly, just like how dragons are unable to comprehend mortality.

The words themselves therefore might be implying just a simple undoing of time to restore the flesh, or it might be something akin to returning the body to the state it was in back in the Dawn, back to its prime when it was new and freshly shed from Akatosh. If it is more of the latter, I could see it being an ability reserved for Alduin himself as it seems like something only the largest, most powerful shards of Aka could accomplish, but the act of restoring flesh is more mundane, something a regular old dragon could reasonably do should he know the words of power. As for why they don't, it could be that Alduin was keeping the shout to himself, and would take down any follower of his who tried to use it, seeing it as an act of insubordination.

What about Argonians? They don't comprehend linear time like the other races, and instead see the past, present, and future as the same.

My personal impression was, that almost any dragon could resurrect any other.

But most of them did see themselves as goods, and do not really want to accept anything lower.

So, they are happy if Alduin do resurrect them AND promises that he will restore the old times. But no other dragon would resurrect them into a world where dragons have to hide, since they would not accept that fate.

By the way, I find it very majestic if a dragon flies in the heaven. A world where dragons would try to keep the peace would be fine.

Well... logically speaking, he likely traversed all of nirn and revived all of the dragons.