onestly i think teh whole debate of intelligent life forms and first contact , ect ect , is all relaly pointless , stephen hawkings and most posters on ehre are thinking in human terms .. consider this
what is your opinion of , say a dog , a cat , what about an ant , or a differnet small insect ??? do you consider anyof those as truely intelligent ???
give it some thought , in all likely hood any alien race that makes it out here , might not even reconise humans as being an intelligent species their entire concepts of life , culture , religion and what constitutes intelligence might vary so differntly from ours that we don;t register on their "radar: as any thign other than another animal , that if they even reconise us as "living organisms: . they may be sillicate based and there for have a completely different definition of what constitutes as "living" , ior they may jsut simply think of us as crude animals. who knows.
i hoenstly think that there is most likely other life forms (aliens) that are similar to us , but given teh vastness of space ,i think there also are just as many aliens that are truely "alien" to us .