Oh God. Where do I even begin? The games that outright sucked, the games that I never got around to playing, or the ones that I wound up clearing out in a day?
Though on consideration I've done very well about not regretting game purchases in 2017! This past year I've only had one regret, Cave Story+ for the Switch. Great game, but I paid 4 times the going rate everywhere else for a game that is really old just to have something besides Zelda for the console when I first picked it up back in June or so. Previous years were loaded with endless examples of games I didn't have time for, or only played so far after release they were down to 10-20 bucks after I paid full price.