Pranams. No doubt "Suryopasana"is the best of all upasanas because of its mention in the vedas.But,there are other forms of upasanas.There is Ganapatya,Kaumara,Bhagawathya(Devi),Agneya,Chadra,Varuna,Sarpa(Naga),Aindra etc.which were followed before.But,only few are being followed now. N.Srikanta.