if im thinking the same question as you, then wouldn't their presence be enough of an answer? i dont wanna argue religion, im christian, but im not the kind of fox who just pushes beliefs on other people, i let them believe what they want, with no judge...
as for me... its really a hard question, cause the thought of bringing someone back... their time had passed, so bring them back would cause a hole in the universe, slowly destroying everything till there's nothing unless they we're to die again... but, at the risk of all that, probably paul walker... i dont like him personally, not a fan of his movies. but i know it would make a lot of people happy if he came back...