Did you actually read what I wrote? I never said Aquinas slid from optimism to pessimism at all. I summarised his teaching on the sins against Hope, Despair and Presumption and gave the source in the Summa Theologiæ. 
Hope itself is optimism based upon the promises of Christ.
Nowhere did I object to the idea that eternal salvation will be a better experience than life here on earth. Have you never heard the simple explanation in the Penny Catechism of,  "[man] being happy with Him [God] forever in the next [world] and the Beatific Vision?"
Genesis 1 does not say that life itself is good, it says that God's mighty act of Creation is good, "...et vidit Deus quod esset bonum."
Everything God does is good because God is the absolute 'good''.