ongoing is an adjective describing "continuing to exist or develop, or happening at the present moment".
go on is a phrasal verb meaning "happen" or "continue".
go on its own doesn't really have any suitable meanings: the closest is "operating". So you could say "Is your watch still going?".
If you want to describe a television show, you probably want an adjective:
The ongoing television series, "the Simpsons"....
If you want to ask whether it is showing at this moment, you could use the "happening" meaning to ask
Is "the Simpsons" going on?
If you want to ask whether the series will continue in the future, you could use the "continue" meaning:
Is "the Simpsons" going on after the current series?
If you simply want to ask whether the series is currently being aired regularly, you would be more likely to say
Is "the Simpsons" still running?