I think people appreciate each differently.
Rent is like the serious older-brother that teaches you everything. Everything sad usually happens to him.
Wicked is like the cute younger brother with whom you can play and have a good time.
Both shows are so radically different but they both have that "rock" music type score (Rent more so obviously) instead of the more traditional Broadway scores of Sondheim and Webber...
I definitly agree, and I think a lot of the connection does stem from Idina as well (kids hear / see Wicked and then find their way to Rent or visa versa)...but for me, at least, the reason why I love both musicals is because they are different like BSoBW2 described. When I am in the mood for bubbly happy etc. I listen to Wicked, but when I need a deeper and more intense sound I listen to Rent. They are similar enough in sound that someone who likes the style of one can easily listen and like the style of the other, but at the same time they are meant for different emotional points in ones life.
If that makes sense...
"If you can talk, you can sing...if you can walk, you can dance."
- T.K. Greene