The political drama, which starred Martin Sheen, Rob Lowe and Bradley Whitford, was broadcast on NBC from 1999 to 2006.
Promoting his new show Shameless at the Television Critics Association's winter press tour, Wells said: "It took us a long time to sell West Wing at the time, and I think it would be completely impossible to sell it now to network television. You would take that show to cable [these days]."
However, the producer added that competition from cable is forcing network television to take more risks.
"I've noticed an increased willingness to take risks at the networks and try different things," he said. "The network numbers have come down and the cable numbers have come up and the audience is now looking for their shows wherever they can be found.
"But we would never be able to sell [ABC's '80s Vietnam War drama] China Beach to a network now. I would never be able to sell ER, actually, which was hard to sell to a network at the time."
The West Wing creator Aaron Sorkin's new show The Newsroom will air on cable channel HBO later this year.
> Jane Fonda joins Aaron Sorkin's HBO newsroom drama
Watch HBO's new drama trailer - including clips from Aaron Sorkin's The Newsroom - below: