I just looked it up. You get all the characters from all three versions in 3.0, but you don't get the playsets. And you get 2.0 and 1.0 characters with 2.0. You can't play newer characters or newer playsets on older versions of the game.
So the only reason would be to play those playsets, but you'd also have to play on that game alone and not use newer characters.
I own a lot of figures and all three games on consoles, so I can give you the run down. These games were my kids first video games so I have a real soft spot for them.
Yes, the older characters are included in the newer games however you essentially cannot use those characters unless playing in the sandbox ("toy box") --story/missions/structured levels are set up so you have to use universe appropriate characters (only marvel characters in marvel levels, only star wars characters in star wars levels, etc).
1.0 is all Disney/Pixar content for the actual missions/levels. There you have Cars, Toy Story, Increadibles, Monsters University, and Pirates of the Caribbean. There's some great content in there
2.0 is all Marvel so there's Guardians of the Galaxy, Avengers, and Spider Man. There's also some cute tower defense sort of mini game and a top down diablo style mini game which you can play in either the a Stitch/Brave theme or a Thor/Guardians theme. It's pretty good.
3.0 is probably the best value. It has three star wars games (one based on each era of the star wars franchise), an inside out game, a kart racing game, and a Diablo style game that lets you play as any character. I cannot recall if they ever released the finding Dory content for PC.
The toy box is really neat as you can make your own levels and even wire up game logic, but what's possible in the 3.0 toybox blows the other two out of the water. Plus you have access to Tous/set pieces from all three games.