This shows you quite nicely what all the alt-coins did during the previous two run-ups. You can see that they all mostly jump with bitcoin and then slowly descend as their bubble fades...

http://bitinfocharts.com/comparison/marketcap-btc-ltc-ppc-doge-nmc-qrk-ftc-nvc-vtc-wdc-trc-frc.html

press the log button in the bottom left corner...

http://i.imgur.com/PrnlqwO.jpg