If you're really only interested in coins that are at least two years old then Peercoin is the only option that both brings something new and useful to the table, and meets your age requirement.

Keep an eye on BitShares through the next year until it's birthday. it's getting close to a year old. that's my pick.

i'd keep an eye on Nxt, Ethereum, and Counterparty until they meet your two year requirement as well.