I would view abandoning this property as being a positive move, but it would only be half the battle. Sony needs to abandon the Killzone franchise as well. While Sony does need a flagship product in this genre. It is becoming quite apparent that neither franchise is fitting the bill. As being a Halo killer, Gears killer, or Call of Duty killer. This would be a logical prelude to fashioning a new franchise. One that may have more resonance with gamers.
Sony shouldn't be settling for the ninth or tenth best selling franchise in this genre. They really need to be at least in the top five. If these titles are hardly sticking with their own customers. The truth is they aren't going to bring in the new customers that Sony needs moving forward. Sony needs to start over, and try to build something new. It also shouldn't just concede this share of the market to Microsoft.
Look I neither love or hate Resistance. It is apparent to me however that Sony should be trying to mimic what it is that Microsoft has done with Halo. Namely creating a franchise that can support a expanded Universe. Microsoft has a lot of synergy going with Halo, and if Sony had even half of that with Killzone, or with Resistance. Then the games would be selling better, and more money could thus be going into development.
Sony doesn't just need a great exclusive shooter. Sony needs to generate a strong franchise, and the Universes at play in their games are obviously not compelling enough to really engage gamers.