I do have to disagree with you - not a single one of those IPs you mentioned even has the potential to be a Mario or a Zelda-level franchise. When you can make God of War Tennis or Super Smash Ratchet and Clank and sell craploads just because of the mustacheo'd guy in suspenders on the cover, then we'll talk. Mario games don't just sell well because we all love Mario - they sell well because we *KNOW* they'll be good. Most people wait for a few reviews on Ratchet and Clank before picking up the newest title in the series. Most of us already have pre-orders on Super Mario Galaxy 2 (or would, if such a thing existed).
How many of you have re-purchased the original Super Mario Bros, either in GBA or VC form?
How many of you would purchase the original Gran Turismo in emulated form?
I'm really not sure that's a valid argument about Sonys lineup being weak just because they don't have a Mario or Zelda-calibur title. That's like saying that Nintendo's Mario and Zelda games are weak because they can't sell on the scale of Carnivale Games. For one thing, although those games are generally between "above average" and "exceptional," I think Nintendo's success with their franchises has less to do with the quality of those games than the fact that they are a big fish in a relatively small pond. It's like asking climbers why they climb Mt. Everest: people buy them because they're there, and they're better than the rest of the crap in that genre on that platform. Think about it for a minute: what 3rd party games can you think of from the N64, GameCube, or Wii days that are actually comparable in quality to a Nintendo-made game from the same genre (note: I said "3rd Parties." Rare doesn't count on the N64 since it was 2nd Party)?
For example, let's take the success of the Mario franchise. Can you think of a single notable platformer on the N64 that wasn't made by Rare? How about the GameCube? The Prince of Persia franchise quite definitely, but that's the only one I can think of. How about the Wii? Let's do the same for Zelda, and once again I can only think of one notable 3rd party venture in the adventure genre that was notable, that being Beyond Good and Evil. You might argue Okami on the Wii, but the sales certainly haven't proved that one comparable. I could do this for every genre on all 3 of its most recent systems, and only be trumped in a handful of categories they have games in (notably RPG, Music, and Party games). Nintendo has made mediocre games in its core franchises in the past (Mario Sunshine and Mario Party, anyone?), but they sell well regardless because Nintendo has a history of making at least decent games and 3rd Parties have a history of not putting in the effort to compete with them. That's why I think they sell as they have. As strong a development house as Nintendo is, there's just no quality competition.
By contrast, I can think of 3 strong platformers on the PS2 just off the top of my head: Jak & Daxter; Rachet & Clank: and Sly Cooper. By contrast, Sony's market has greater diversity and thus the sales aren't as strong by contrast. While they are published by Sony, the developers themselves I believe are 3rd Party. There's loads of competition by comparison.
Sony's big problem when it comes to the games on their platforms is that they are not a strong development house, and have always lived & died by the quality of their 3rd party exclusives. However, with the exhorbitant price of the PS3; it's relatively-small user install base; and the rising cost of game development, 3rd parties can't afford to be just exclusive to them anymore. So now Sony doesn't just have competition within its own console's library, but competition with the same games on the much-cheaper and graphically-competitive XBOX 360. They struggle as a result, but it's not like they don't have good games. They just have few games that require a PS3 to play that are worth playing.