One similarity is that they are both small. Viruses are a lot smaller than most bacteria, but they are both really small compared to your pen tip.
Another similarity is that they both have the capability of making you sick.
Appearance: Viruses come in a variety of shapes and designs. Most of the time they look completely foreign. Some viruses are symmetrical, but some are not. A bacteriophage virus, for example, looks like a space ship with legs. Bacteria, on the other hand, do not widely vary in shape and appearance. They are cells, so they are mostly roundish.
Reproduction: Bacteria reproduce through binary fission, which is a form of asexual reproduction. Viruses reproduce by either the lytic or lysogenic life cycle. They differ slightly, but viruses survive by hijacking a cell. In that regard, viruses are parasitic.
Structure: Both viruses and bacteria have an outer "shell." The difference is that bacteria have a cell membrane and viruses have a protein shell coat. Both entities have DNA stored inside of the outer barrier.