John certainly isn't a "fancy" player, but he keeps the beat and doesn't only stick to the root note
I think he's playing and mellow sound was very right for Dire Straits. However, his live sound in the early days is probably some of the worst I have heard ... And the little progression he used during Tunnel of Love (when the song starts building up again, before the grand finale), a 1-3-5 progression in the key of F, that's just downright corny. Sounds like a cheesy swing thing.
Having said that, as great as Glenn is, I'm sometimes a little surprised about his choices. He really overplays at times and sometimes puts in some pretty weird stuff, chords even, which I'm not so sure is all that fitting. But - easy to say for an amateur armchair musician haha.