Jaipur is a great card game with some different elements. Small, portable, two player. Easy to understand but has great replay value. Splendour can also be played two people and its small as well. Bananagrams, Monopoly Deal, Skipbo, Phase 10, Spot it, all fairly quick and fun games, all small for travel.
Sometimes we buy games at the thrift store and just take out the cards to play with, this works for trivia games, guessing games, fill in the blanks, basically any game you just read off cards and don't necessarily have to keep score with a board. This is great on long road trips too.
I have a pretty good collection of modem games, but most are larger games you wouldn't want to travel with.