I think simpler life forms have no chance of surviving long term. Though now that I think about it, you could say caring about that is anthropocentric too. I don't think it's possible to truly be objective because it would require us to escape our own perspectives, but there should at least be some objective measures for this question. Without that, the question is meaningless. Number of species, average lifetime and average happiness seem sufficiently objective to me.
Simpler lifeforms have been one of the most persistent and successful lifeforms on Earth, with a way longer existence than mammals. In fact, some theories postulate they are capable of interplanetary colonization, something we still cannot do!
You're right. I wanted to make a point how it's possible to have an objective comparison between life forms, but I judged simple life forms too quickly. I still think there are some obstacles simple life forms won't be able to overcome, but it's not obvious (to me) which of these have a better chance of surviving long term.
