I tend not to bother writing about the standard big controversies of the day. It's not that I don't care, or don't think they're important, but most of what I have to say about them is being said perfectly well by other people, and most people already have well-defined views on them, and many other forums in which to air those views if they're of a mind to. But I do venture into that territory when it's warranted, and I think in this case it is:
My answer: yes.
Ok, you can argue that their music should not, strictly speaking, be called "rock and roll." But if, e.g., Madonna, The Four Seasons, and the Bee Gees, are in there, ABBA very much deserves to be. Just call their music timelessly brilliant pop, if you prefer. And don't try to take my copy of Gold away from me. Hier stehe ich; ich kann nicht anders.