That's all relative though. What's memorable for you isn't the same for everyone. The most memorable for me where the original Strat, blackrock spire and brackrock depths and original deadmines, though I wouldn't say they're the best dungeons in the game. I don't think the MoP dungeons were 'bad' but the only one that really stuck out to me was Shadopan Monastery. The rest weren't all that memorable for me.