There are some differences between "free mod" and "stand-alone game" where you have story line which isn't your own and isn't free to use. It should works like Restoration Project, MegaMod or other mods where Sfall is applied.
For more law issues ask:
- Bethesda,
- Gabe (distributor).
If they will have officially agree for free to use this both games (F/F2) then you can do what you want.
These recreated games are free to play at the moment. You can recreate for ex. GTA, GTA 2 which are officially shared for free download by Rockstar. Fallout also was free to download from gog.com few years ago, but from while when Bethesda took Interplay's rights to this title you must pay for it.
BTW all these downloaded copies are fully legal.
Other example of receation is Black Mesa Source game. To run you have to buy atleast Half-Life 2 game where you have first part of this game included and you have bought both - the Source engine and Half-Life story line. After that you can technically install this refreshed and improved remake of Half Life game.