Yep, BTC for the solid (ish) backbone to your portfolio, NXT for the innovative gamble. (tho I don't really see NXT as a gamble any more, I know whats coming up.....)
NEM looks good for the founders, nice distro, but I don't know if has serious long-term potential. Time will tell, I'm fairly certain NEM will go nuclear when it launches.
My prediction for 2014 is the death of LTC. I got out 3/4 months ago and haven't regretted it yet.
For the rest: look for something with at least a little bit of innovation, make sure that there is a real dev team and community backing in place. Maybe half (or more) of the alts on conmarketcap are just backed up by one sweaty dude in a basement somewhere. (or a raving lunatic...check Marinecoin.)
A coin won't get anywhere these days without a supportive community at least, see Doge for a perfect example.
Why are you not enthusiastic about LTC?
So far, it's been quite constant with BTC pricing. I agree on threading carefuly in choosing alt coins...I got burned with Coinye and Lottocoin in the past. Expensive lesson.