I can't think of an exception that aĵo would mean something not concrete. Here the question is about "stuff", "topics" etc, not about "things" actually. So IMHO it wouldn't be the same.
Anyway: of course everybody would understand it and it wouldn't hurt people's ears too much. :-)
tomaszym is right that aĵoj is basically reserved for concrete objects. But I actually think both should be accepted, because at least to my mind, the English prompt is ambiguous; English thing can be translated to either aĵo or afero, depending on what the speaker intends (and here we can't tell what the intention is, because there's no context).
I guess what I'm getting at is that when I read this sentence I think, "what are some things that people like?" Some are events/happenings like "going to concerts" which would definitely be aferoj, I should think. But others are indeed concrete things like "pizza," which I would think is closer to aĵo. I suppose you could interpret "pizza" as a shorter way of saying "eating pizza," but that seems like a stretch to me. I suppose the heart of the question is whether afero is really "an affair/happening" or whether it has a much broader meaning. Or perhaps aĵo has a much more narrow meaning than I thought. Any thoughts?