This web-site (http://www.diserio.com/top15-skylines.html) has a listing on the top 15 skylines in the world with some honorable mentions.
I think my favorite is Singapore (pictured here).
If I were creating the list my top 5 would probably be:
2. Pittsburgh, USA
3. Guangzhou, China
4. Sydney, Australia
5. either Dubia, United Arab Emirates with it's desert or Seattle, USA with Mt. Hood in the background.
Feel free to post your top 5..