Older RPG's that have pixelated graphics are hard for me to get into these days. It's not that I can't, but it takes me a lot longer to get past the "eww, 16 color pixels" reaction to just enjoying the gameplay, and sometimes I don't feel like taking the time.
But games like Morrowind still look ok graphically (even if they're not "omg uber eyecandy" now) so if I could make myself play it again, I'm sure I'd enjoy it/wouldn't find it boring. But often I don't feel like taking the time to play something I've already played, even if I haven't touched it in 5 years.
The familiarity breeds contempt point is also valid. Even when something is a treasured fave, and even if you don't revisit it too often, eventually it starts to lose a bit of the magic. Sometimes it takes 2 years, sometimes 5, sometimes 10...but it'll happen at some point. It's not that you don't still love/admire/respect the game or that it has to be removed from one's all-time faves list, but nothing stays magically shiny forever.
These days tho, I have more trouble with the "been there seen that" syndrome w/trying to play new games. That is, during a certain period I played so many games in several genres that in recent years it's hard to find one that does the same ol' same ol' in a way that makes it feel fun/exciting again. If you know what I mean. Skills that have different names but still feel the same/have the same purpose (the 3000th version of a freeze, summon, or fireball spell, oh goodie) and new monster skins aren't enough to excite me. Thus I'm finally becoming more of a "graphics [censored]"...when that wears off, I'm not sure what I'll do.