"The invading Aryans did not have Shiva as one of their gods. Instead they absorbed Shiva into their god Rudra. " - Oh yeah? Did you know that Shiva is itself a Sanskrit word? Shiva is Popular in tamil Nadu because he married Meenakshi the doughter of Pandian King and became a Pandian King himself. Also Karthikeya(Muruga) married a Tamil woman (Valli). But you guys need to no that Pandian kings are Decendants of Manu himself who helped vishnu in his Matsya Avatar.
http://en.wikipedia.org/wiki/Manu_(Hinduism)
Therefore it is wrong to say that Shiva is southern god and Vishnu is from north.
