For me, attractive prose has a lot to do with rhythm and flow. I admire writers, even if their prose is relatively lean and spare, who can make the rhythm and pattern work with the tone and mood. Sometimes it is appropriate, imo, to leave an "extra" word in, if it makes the sentence flow better or evokes a particular attitude or mood.
I also enjoy apt metaphors or similes that are tossed out in passing when they imbue the narrative with personality and evoke a particular emotion, whether it be sadness, humor, or passion.
However as Kallithrix said, for me, it has to serve the story, not drown it. Writers who spend too much time describing just how the ice is sparkling in the moonlight (when it really doesn't make any sense for anyone to pause and take note a detail like this at that moment in time) tend to bore me. I don't need page-long description of a winter scene to feel the cold with my own surrogate senses. I also tend to get impatient with authors who take a long time to
tell me something, the ones who are using lots of descriptive language but actually aren't using it in service of moving a scene forward. Too many stationary snapshots bog a story down, imo.
Exceptions always being when the voice of the piece makes even the long asides interesting or relevant to the personality of the narrator or pov character. So maybe for me, the thing that makes writing emotionally compelling (aside from rhythm and flow) is voice. And an interesting voice doesn't have to be pretty. I have read and enjoyed books, however, that others thought were too flowery or laden with description, so maybe it really is voice and personality for me.
It's really hard to explain when writing that some would call pretty works for me, but I know it when I see it
I tend to remember characters and stories better (even then, plot details will slip away with time) more than particular turns of phrase. When I remember exact wording, it's usually because it made me
feel something that brought me closer to the story.