Just by looking at them you can straight away see the differences between them. Cartoon drawings tends to be dull with very little detail as you can see Dexter only has 3 fingers and a thumb. The first thing that many people notices when they watch an anime for their first time is the characters eyes. Anime characters tends to have big glossy eyes. Not just the eyes, but the hair is very important too in anime design. Their hair design has mainly 3 different shades whereas the cartoon character only has 1 shade. Anime characters has a very detailed human figure and the details are flawless from head to toe and even the costumes.
Its not just the looks that are different, but I think anime are more aimed at young teens to adults. Yes, a lot of adults are into anime. Why? I think because of their well art and story. Anime stories tend to have a twist in them and the plots are a lot more complicated than Cartoons.