Namor makes it to either Glads or Surfer then looses probably. Apoc ran like a ***** from Namor in his Annual comic once Namor was refreshed.
Namor has ko'd Savage Hulk, made abomination loses conciousness, had herc in a full nelson(clearly dominating), beat Doom to a plup.
Hed take Thor no doubt.
The thing with Galds is no matter how much he punches Namor, it would really have hardly no effect because of Namors constant rejuvenation in strength and durability.
In Surfers case, i've really never seen him get punched much. I dont know how many hits would he be able to take from Namor. And how would he fair against the electricity? Both him and Glads are faster, but do they contain the same speed while underwater?
Eventhough I hate to say it as a Namor FANBOY!!, but Surfer beats him. BUT, if Namor gets the sacred Trident and Armor of Neptune, he beats Surfer. Then loses to Thanos.