Eye of the beholder, but re-play ability.
I got quake 2 and 3 from my dad for wf and wfa. It was a challenging pitch.
Sadly that shaped a portion of my life.
Diablo 2 wasn't much for content, but my first major grind based game.
Everquest...gd. I never even aspired to end game content, because I was constantly trying new characters, with an internet veil.
WoW was my first pvp MMO experience that kept me coming back and justifying a subscription cost (which at the time my buddy was paying, putting the needle in for me).
Just a few of my favorite games. A game is valuable if you can look back on it and smile. I lack the ability to see it with foresight.