Hard to say which songs crop up the most at our singers circle but I'll hazard a guess;
Raglan Road
Galway Bay (Not the B. Crosby one but.. It's far away I am today of dreams...etc)
The Parting Glass
Carrigfergus

But regular pub or family sing songs where there is no concentration of folkie types usually produces;
Shane McGowan stuff by the assload (great but overdone)
Christy Moore stuff by the assload (great but overdone)
Wonderwall
Beatles stuff by the assload (great but overdone)
Eagles stuff by the assload (great but overdone)

And I still think folk music is alive, well and growing.