Hmm, thanks for all the suggestions. I was more looking into tycoon and sim games though.

Harvest Moon looked interesting, but there is no PC version. Plants vs. Zombies is a consideration, I know I got addicted to it for awhile. I absolutely love the Myst games, but adventure games aren't for my mum. Sim City is probably not the most exciting of games either. Dwarf Fortress looks like an interesting game, however again I just don't think it'd be something that'd interest my mum. BigFishGames.com seems to have some interesting games, I will also check that out!

So, I guess if we break it down; a game that someone can keep continously building upon something, gather long-term rewards, share/help their friends, isn't insanely complex. From what I can gather, The Sims 3 seems like the best bet at this stage, but I only ever played a bit of the original, so I am not sure how it has changed.

Oh, also something that isn't a decade old would be nice. They were great back then, but it's time to move on now. Also note that I chose to ignore the dumb suggestions.