John Doyle plays melody sometimes but he's such a rhythmic force that overall the music greatly benefits when he's playing backup, IMO.
For a couple of guitarists that shine as both lead and backup players there's Arty McGlynn and Tony MacManus (who's also an awesome fingerstylist).
Also, you have fingerstylists like Donogough Hennesey, Tim Edy and Steve Cooney who play a good amount of melody while backing.
Please excuse any mispells.