I loved every minute of this as I alternated between loving and hating Tom.
I think the reason why we can associate with him is because he is the only strong character in the story; the others drift and dissemble but Tom Ripley acts. His actions may not be legal or likeable but at least he does something.
Highsmith writes brilliantly. Brilliantly; there is no other word for it. The intrigue and suspense builds bit by bit until we find ourselves behind one of the most evil men in literature. Let’s not forget that this ‘likeable rogue’ has taken money under false pretences, murdered his friend and assumed his identity and deceived or killed anyone who comes close to knowing the truth as he lives it up on stolen funds. But he is still likeable. What a feat.