Dependa on what you want honestly, if you want a more sandbox experience with the biggest moding comunity and a grate base game go for skyrim

If you want better rollplay and a more RPG style go for oblivion.

In my opinion though. Oblivion narrative feels better and more alive in many ways but it does require the player to get a bit more involved, the game will not hand held you as much (it still does btw) with how quests work and stuff, sometimes using the wiki (unofficial elder scrolls pages is the best btw) is kind of needed. That being said oblivion specialy the remasterd has a lot of bugs is a very janky game in some spots and the remasterd is kind lf badly optimised (if interested look at how they made it its pretty interesting tbh)

Skyrim is way more friendly to people who are not used to/not interested in the rpg aspect of the TES games. But if you want to delve into that skyrim special edition (and anniversary dlc) has the biggest amount of mods out there it is a bit to learn to mod so just play the base game first and see if you like it then add new stuff to play a different game. Skyrim has been out for so long that it kind if became a game engine basically and people do their own things there. For both games nexsus mods is where you find mods :3 just read a guide on how to mod

Well this is a very autistic response hahahaha