Yeah, that would be stupid.
At this point softwre-wise I find more honest to focus on exclusives. You want to play Halo or Gears? then you'll need a 360. You want Uncharted or LittleBigPlanet? then you'll need a PS3.
I disagree, I think at this point in time its more dishonest to talk about exclusives. In general the people who talk about exclusives seem to have already made up their mind about which games are really important to them or play so many games that having extra 'good games' in the library available to them is a bonus.
People generally don't know the value of a game to them ahead of time. They can also make do with an equivalent or lesser multiplat/exclusive substitute as well. For example, someone who doesn't have access to Halo 3 may simply play Call of Duty 4 instead for the PS3. For the people that Halo 3 is important, they have likely already made up their mind to get an Xbox 360. For the people who don't have access to Gran Turismo, the only people who would be upset really are the people who already made up their mind to aquire or already own a PS3. The rest of the population would likely be about as happy playing Forza 3 instead.
Its a case where you cannot tell people what they will want. So unless they ask in the first place and come up with some specific requirements its quite likely that by listing a bunch of exclusives you're not helping anyone but yourself and padding your ego.