If you are thinking only about appreciation then you are going to be disappointed. Even natural born children don't appreciate you.
I love it. You are so right.
Good advice I received about being a step parent was to be a friend and an advocate, but forget about ever really being "parent". In our case, the boys' mom has been abusive, negligent (moved away and never calls let alone sees them). The boys are 17 and 19 now and haven't lived with her for over 5 years and haven't seen her in over three years . They have moved from being blindly loyal to their mom, which although not really deserved, is surely expected and natural, to being sadly realistic about her ability to mother them well. I know though, that even though I have loved these boys and nurtured them in every healthy way, when it comes to crunch time, I am still Trish, not mom and never will be. Respected yes, authority, no.