Most people would word it differently. For example:
Don't stop him, I want to hear this.
Hold on, this is interesting.
Wait a minute, I'm enjoying this discussion.
Just a moment, I like his explanation.
I'm enjoying his explanation.
I want to hear what he's got to say.
"I like his talk" doesn't work well here. Usually a person's "talk" refers to a relatively formal presentation they're giving. It's also possible for people to share a talk or discussion, but then you wouldn't say "his talk". You could say "I like the talk we're having". Even if in practice it was a one-sided discourse, it would sound a bit odd to refer to "his talk".
"I like his conversation" might work, but is a bit too formal and would refer more to his conversations in general than to the particular instance.
"I like his speech" could mean that he was addressing a conference or a rally and you were enjoying what he was saying. In the context of a conversation, though, "I like his speech" would sound very odd indeed, as though you were praising his particular way of pronouncing or enunciating words rather than what he was actually saying.
"I like his word" would mean that you liked one particular word that he kept on using.