For me it's the artwork. Anime style seems to be different than cartoons. For me when I think about cartoons I think about Looney Tunes or Tom and Jerry, something like that When I think about anime I think about things like Naruto, SAO, FMA, with that specific artwork style.
Also like @Animedragon said too it's the storyline. Anime seems to have an actual storyline with things progressing with each episode like a normal T.V show would, and when I think about cartoons I think about something that doesn't really have a storyline that goes from episode to episode.