Viruses and bacteria differ in several respects.
Bacteria have ribosomes and can therefore make proteins on their own, viruses can't
Bacteria have polymerases for making copies of their own DNA, most viruses hijack cell-
machinery for DNA synthesis (though some viruses can transcribe their own
genetic material)
Bacteria reproduce through fission, budding, etc while viruses are built in the cell
Bacterial genetic code is always DNA based while viruses can be single or double stranded
DNA or RNA viruses
Bacteria have a metabolism, while viruses don't
Basically, viruses are very, very simple forms of life. They lack many of the necessary components for replication, which is why they must infect, hijack, and use a host's cellular machinery for their own purposes.