Why do we have nostalgia for objectively bad games?

For my 12th or 13th birthday(I've slept since then), I spent $10 of my birthday money on two games I couldn't believe existed! Mega Man 1 and 3 for the PC, and they were compatible with my Tandy 1000! "Score!", or so I thought.

When I got them home, the reality set in: These were NOT Megaman 1 and 3 as I knew them. The graphics looked...wrong ,there was no music and very few of the classic Mega Man enemies weren't there.

Mega Man 1 has only three very unusual Robot Masters and you had to beat an intro level before you could select a stage.

Mega Man 3 had proper roster, but the robot master all looked like weird bootlegs. Mega Man can swim now, for some reason.

Now, when you spent money on something back then, you played it, even if it sucked, so I soldiered on with these. Managed to beat 3 at one point.

Looking back, I have some weird fondness for those terrible old games. Why is that?