I would say yes, on the grounds that it fits the definition. I'm actually not entirely sure why religion wouldn't be considered a meme.
Not to put words in the mouths of my intellectual opponents, lest I accidentally argue too well for their side (which might sway people the wrong way [I can be persuasive at times]), or argue their case poorly, and thus be guilty of the straw-man fallacy, but I will give some reason people might disagree.
1) Religion is the word of God. Thus, it did not evolve from other ideas. It is divine truth in its purest form.
2) ... 1 is the main reason actually. But within 1 there are subtle variations. Some would argue that religion does not follow the rules of evolution in the ways that gene's do. Others would claim it has too high a copying fidelity to evolve. Other still might have other subtle variations on this that are not just semantically different, but really are different concerns.
Well, there is a 2nd reason people would argue religion is not a meme.
Religion doesn't think or make decisions, or even directly manipulate the world.
Religion only exists within the brains of people who subscribe to it, or on paper. Not everyone who knows about religion agrees with it, and it is true that some of the people who understand religion the best are those who have been fighting it the longest.
Thus, they would claim that it is non-sensical to claim it is a meme, because really, the parallel breaks down. How does the pope figure into this, or witch trials, or heresy, or bibles, or the crusades? How do you reconcile the fact that religion, without people, not only cannot spread, does not exist (according to someone who feels it is a human invention).
You see, it may seem obvious that religion is a meme, but strong arguments can be made by either side.
I feared that those who feel religion is a meme would say "It is a meme, and I don't need to explain myself because it is obvious", and on the flip side of that, those who feel it isn't, would be intimidated by the attitude of those who think it is.
I would like to urge you not to let this happen. Both sides have strong arguments to make, so, by all means, make them.
Please nobody go "I am right, because it is obvious" or "I am right, because it is true."
After enough time has gone by, I will weigh in on the side of "It is a meme", with what is likely to be a very long treatise that works in lots of biology and history and game theory. Until then, please don't mis-represent either side.
Also.
NO FLAMING. I will personally report you to a moderator myself, even if I agree with you.