While I generally agree with you (and want to warn you to never take Spwolf on in a logical debate...it'll only cause headaches). I have a few faults with your statements.
1) While this is generally true, its not absolutely true. There are instances were PS3 games are beating 360 games from a similar point of life. The biggest two differences has been that the PS3 hasn't had any major titles take off in sales and changes in how we get data has limited how much of the PS3's sales we actually see. With Resistance leading PS3 software sales, the 360 is destroying it at the upper end, but the lower ends are not all that different. November '06 for the 360 was a lot like November 07 for the PS3... neither did so hot. It had 1 first party game sell a million, but only 9 other titles sell above 50k (only one of those above 150k). With the limited data we see now, if you wanted to compare third party sales between the two months, you could argue that the PS3 is better for 3rd parties (it doesn't make it true, but you could argue it). We do a lot of that...Anymore, we argue over speculation and assumptions rather than actual facts.
2) That statement is mostly false. Tie ratios change over time but don't always decrease and you can't expect consistent change between two different consoles. Look at the PSP vs DS lifetime changes. The quality of/hype surrounding the game has a bigger effect on how it performs relative to the userbase than any other factor. Look at CoD3 vs CoD4. The PS3 is still young enough that it can still have a large enough shift in its demographics that could help these games... 1.2 million new users (more than a third of the total userbase) have only had their system about a month (or less) and we have no clue what types of games those people like and the effect they'll have on software sales.
Personally, I believe talking about tie-ratios is just falling for PR spin. Userbase is what's is important. (which doesn't exactly help the PS3 either)