Last year alts rise a lot. I dont know the average percentage. But when I check coins in the market at year 2013 lots of them dead now (too low ranks). probably new tech coins won them (like peercoin, namecoin, ixcoin etc)
Also we are following new ICO s and most of us expecting too much gain from new coins which are not at the market. If our ICO expectations will happen, when they added to market, current market coins will go down. kind of paradox

I think with ICOs, many of them drop in price but a small percentage have huge gains. If you have invested in lots of ICOs and hold them, this increases your chances of holding one that makes those gains.
However - and a big however - the market has been bearish for so long now, that everything is dropping in price.
If it is a great project and you have faith in it, then you'll need to hold until development has reached a stage where the project has a live working system and can gain some price momentum.