I think the Straka-Nylander-Jagr line is easily the best since the lockout. However, every year it seems at least for a handful of games we have a line doing amazing things on the ice. Unfortunately if that line had a poor shift under Torts it got broken up (not too much of an exaggeration). I remember Anisimov-Stepan-Gaborik doing amazing things for a few games. Hagelin-Richards-Gaborik was really good.
We have the Stepan line now and they're probably our most entertaining line since the Nylander line, but I don't know if I'd say it's #2. None of the guys are goal scorers and they have 8 goals total between them. I feel like they control play better and more consistently than that Hags-Richards-Gaborik line had, but that line had a 40 goal scorer on it. I think Richards is a better goal scorer than Stepan too. At least he was that year.
We haven't really had many consistently used lines since the lockout. Most of the lines people are talking about only lasted for a couple of weeks, tops.
It may not have been an offensively gifted line, but one line that stands out to me that was almost always together for a very long time was the Prust-Boyle-Fedotenko line. That line would keep the other team pinned for minutes on end, wearing down defensemen and drawing penalties, while chipping in a solid number of goals.