It really depends on what factors are important to you and how you weigh them as well as what appeals to your tastes. The Ghost Recon titles (90.7%, 88.4%), Call of Duty titles (90.0%, 83.3%), and FEAR (84%) have all been well received by critics, which all compare similarly to RFoM's 88.2% average review (all gamerankings.com). If you include shooters in general you could add in Gears of War (93.8%), and seeing as most FPS fans would be at least interested in Gears it is relative (as gamers tend to go for the best games on a platform). Each of those games has strengths and weaknesses, like Resistance, and it can be a matter of taste. Some people enjoy the amazing feel of CoD2 and the non-stop onslaught of excellently scripted warfar, others the tactical warfare in Ghost Recon and the more "steady" pace of online (overlooked a lot imo) and others the impressive AI and story/cheap thrills & chills in FEAR. So what is important to you will really determine what sticks out as the best as well as how important the flaws are. If the flaws are irrelevant to your tastes it won't even matter.
Personally I look for the sum of innovations/evolution (which don't always need to come in big packages) and if the gameplay is well designed (levels, weapons, design) and if it has an engaging, fun experience that can draw me in through the story. Very, very few titles do this and tend to insult you with poor AI that doesn't hope to do much outside of run and kill, if not with a variety of "intelligence" in regards to take better cover or coordination (and most FPS do have poor AI, but it is relative to eachother and execution... my hope in FPS titles is that they know their limitations and then design around them with the goal of accenting gameplay and the story with believable AI for the circumstances, hence I liked HL2's AI better than Far Cry's due to execution). MP is pretty important to a games value these days, but just having a lot of players doesn't mean much in itself (BF was superior to the OF games even though they had a lot more people in the later) but again how it is designed, balanced, and plays out. Taste will always be a factor but most online games don't have staying power not because of lack of features but lack of execution and the "addictive" gameplay balance as well as the intangible "easy to pick up, difficult to master" design as well as the engaging factors that pull you in but are deep enough to reward you for coming back.
Anyhow, using objective benchmarks the Call of Duty, GRAW, and GeOW have all done commercially well, critically well, and had robust online activity which makes it hard to flat out say Resistance is the best or even most complete. It depends what you put first in your priorities. What is most relevant is that the PS3 has a new franchise that fills a genre of need and is very solid in SP and MP. It is something to enjoy now and build upon for the future and it is the best the PS3 has to offer. Kind of unfair to even begin comparing it to 360 titles because it isn't a one to one comparison to begin with for fans of this genre (hence why it has taken a lot of time to convince PC-FPS gamers to take console FPS seriously at all).