I think that popular usage fairly clearly indicates that there is demand for a term to refer to highly contagious ideas. I think they should be called "supermemes".
A rather obvious way of classifying memes is according to how popular they are. So, following metric-system conventions, we might call memes with more than a million existing copies "megamemes" and memes with more than a billion existing copies "gigamemes". In the future, we may see "teramemes".
However, for an umbrella term to refer to "very popular" memes, I think "supermemes" is the best term. Supermemes may be highly contagious, very persistent - or preferably both.
It seems likely that the culture of today is relatively poor at occuping human brains - compared to what will be possible in the future. So maybe most of the "supermemes" are yet to come. However, it seems as though there is no point in reserving the term for future use. Some of today's memes are "super" enough.
I note that others have previously used the term. For example, Rebecca Costa says:
Supermemes are ideas that have such strong support or opposition that the mere mention of them clouds peoples' thinking or prevents people from even looking at alternatives.That's close to my proposed usage. We both have the basic underlying idea of a powerful, successful meme.
One possible problem is the mismatch with the concept of a Supergene. It looks to me as though that one should yield. It seems generally better if "super" refers to fitness rather than mere size.