It's that 10% of platform exclusives that make the difference.
Obviously the guy likes MGS, so assuming he's looking at what's available today, why buy a console that doesn't have what he wants? He already mentioned Uncharted and R&C (three games, good as they may be, are NOT reason to jump ship if you already have a decent collection on another platform).
You can always sell a Wii today for what you paid for it, and pick one up in a year or so when they're cheaper, but most of the big franchises for the platform are already out, making it pretty easy after two years to decide whether the Wii is for you or not.
Keep your games unless you really don't like any of them, which I find pretty hard to believe for a self-professed long time Nintendo fan.
You can hold your breath for improved 3rd party support, but facts remain, the best third party support is not on the Wii today. And based upon the laundry list of games in development currently, it won't be on the Wii tomorrow. Big budget 3rd party titles (if that's what you want) for the Wii aren't made simply because they wouldn't sell any better than a game better suited to the platform, made at a fraction of the cost.
If the motion controls of the Wii haven't magically re-invented gaming for you, then there is no other appeal beyond tried and true Nintendo franchises that you either love, or are indifferent to.
You can hold your breath for Wii 1.5 with Motion Plus, but until we see dedicated games that were designed from the ground up that REQUIRE M+, that prove the worth of the feature (which will not be done in a year or less) it's just not a system seller.
IMO, don't bother buying a PS3 until you have a decent HDTV.
Sure, you can still play the games on it, but they were not designed to be output at 480 lines of resolution. Text, resolution viewing distances, fine detail, etc. all downscaled/lost.
You'd be far better off playing your games on a PC monitor with HDMI inputs than an old 480i CRT TV.