A few things:
- It's Batman and Robin.
- There's a period missing from the second example.
- Friendship is usually between two people, not of them.
- Superman's appeared together with Batman more than Robin has and, being comic characters, there are various arcs where any of the three are trying to kill the others.
Now, that said, "A true friendship endures forever, just like Batman and Robin's", isn't completely wrong even if "True friendship—like Batman and Robin's—lasts forever" is tighter. You want B&R to modify "friendship", not "forever".
edit: I don't have enough reputation to post more than two links, apparently, but you can google for fivethirtyeight, superman, and batman to get Walt Hickey's breakdown on the numbers showing that Robin is Batman's second love, not first.