I think it's best to focus on cryptos that have a shot at longevity. LTC is obviously one, but there will most likely be 1-2 more coins that will be there for the long-term. Ability to mine via GPU in for the duration of the mining process will be a big part of a coin's long-term viability, IMO. Obviously BTC has a flaw in this area, but there are still plenty of people willing to mine it via asics.
Maybe coins 3 & 4 haven't even been developed yet, but I'm curious to hear from you guys if you think any of the current crop of coins has a shot at long-term usage right alongside, and complimenting BTC & LTC.