We can discuss if Prometheus and Covenant are good films... If Ridley should direct the next Alien movie... But the thing that we all must be agreed is that Prometheus should had been like the Jon Spaihts script, the direct Alien prequel.
But talking about the two movies that we get, I really liked Covenant. It's easily the best film since Alien 3. Prometheus O want to like it but it was a big disappointment and the troubles that it have aren't easy of ignore. About David being the Alien creator, I don't think so, I always looked it like David only copied and continued the work of the Engineers.