oh wow....this one is easy; countless HOURS and HOURS of 8 bit graphics, and thumb numbing excess to the point where the controller would wear down on one side or had a bunch of gunk stuck between the buttons.
My favorite game?
TECMO BOWL!!!! For the old Nintendo system!
Day in and day out, we'd fight over the game - actually, NOT the game, but the TEAM - YOU ALL know which team I'm talking about!
With Walter Payton on your side, every other play was a left side sweep with no defense able to ever catch Payton on that run. I remember having games with the score being something like 150 to 0, all rushing touchdowns by Payton; always the left side, running alongside the line, and never getting caught by any defenders.
Ahhhh....the good 'ol days!