Re: I uninstalled Origin before uninstalling the games on it..
@MrAmir2121 If you plan to uninstall the games through the Control Panel, then yes, there could be a difference. When uninstalling a game, Origin also removes related registry entries, at least some of the time, whereas the Windows uninstall process may not. So using Origin could be more thorough; I don't know whether this matters for your own purposes.
If you don't want to reinstall Origin and go through the process of locating the games, you could use a tool like Revo Uninstaller to completely remove each game. (There's a free version.) Revo will search your entire computer for stray game-related data and is more thorough even than Origin.