So i have many friends that randomly swing by with their laptops and we want to game. sometimes there isnt a game we have in common so I go to look at GOG since older games will run on almost anything. Is there an easy way to find only the games that do multiplayer? Im thinking there should be a browse games option that only features MP games...

In the catalog (Browse Games) there is an option called Game Modes where you can select Multiplayer and Co-Op.