My favorite altcoins are Ethereum, Ripple, Monero and Litecoin. I think they have a very important role in altcoin world and they also show a rapid development by launching some excellent projects with their technology. I think they have a good future.
Agree all the four coins you have mentioned are the best in the business at a moment and even in future they would be very promising and my majority of investment is in ETH as I believe that it has an ability to take over bitcoin in future.