Fallout 3 is very similar to Skyrim.
I’d suggest that.
If you’re comfortable with modding, in suggest “A Tale of two wastelands” as this merges fallout 3 and Fallout New Vegas into a single game.
Fallout 1 and 2 are very different games. Good, but nothing like Skyrim.
Fallout 4 feels very different, not in a bad way but it’s not got the charm of Skyrim or Fallout 3, that lovely feeling of finding things in a flawlessly crafted world.

Ixion
Thought it was another generic fun little city builder.
And it is only it has some absolutely unique mechanics that are fun, a really good approach to unlocking through research, and a genuinely beautiful setting.
Seriously, the music, the story and the voice acting make it a genuinely rich experience.
My Picks…
Deus Ex (So many games try to be this and fail)
Cyberpunk (This one eventually measured up)
Alpha Centauri (Innovation mixed with familiarity and setting)
Fallout 2 (they’re all good. Fallout 2 is special)
Kotor (Star Wars story telling in a beautiful way)
Baldur’s Gate 2 and 3 (I’m stunned that 3 was a worthy successor)
Homeworld (One of the World’s truly beautiful games)
My problem isn’t finishing them.
My problem is starting them.