But there's a deeper problem with this analysis: most people are at least somewhat picky about the games they buy. For instance, if you look at the best-selling Wii games on Amazon. While there are a few game rated less than 4 stars (Wii Play, Wii Music, Super Paper Mario, etc.), none are rated below 3 stars. Most of the best selling games are also critical successes and loved by customers. The percentage of Wii titles that are shovelware doesn't matter as long as there are enough good games to keep you happy.
Which brings us to the question of how many games does a console need in order to be worth the initial cost of the system? First, let's assume that going to a movie is the standard for measuring the price people are willing to pay for an hour of entertainment. In 2009, the average movie ticket price in the US was $7.50. It's probably $10 or more in Southern California where I live, but let's just go with the national average. By general rule-of-thumb, the average movie length is 120 minutes, so the standard hourly rate for entertainment would be around $3.25 an hour (or $5+ in LA).
Now the Wii currently costs $199 and includes both Wii Sports and Wii Sports Resort, which is a pretty amazing deal. Divide the cost by the standard entertainment rate, and it works out to about 61 hours required to break even (or less than 40 where I live). According to the Nintendo Channel, Wii Sports averages just under 38 hours of play per console connected to WiFi. Wii Sports Resort averaged almost 19 hours by December, 2009. That means the current bundle is already likely to be worth the cost without considering any other games.
But let's say you don't think you'll play the Wii Sports games that much. Super Smash Bros. Brawl very nearly makes up the initial cost of the Wii all by itself (75+ hours). Don't forget that each game adds to the total cost of ownership, which means the extra $50 adds another 15 hours or so to the break-even-time. I'd also have to guess that a significant percentage of Smash Bros. game time is in multiplayer, so you need to add in the cost of extra controllers. (This applies to the Wii Sport titles as well, by the way.) On the other hand, each hour spent on a multiplayer game is worth one hour times the number of players. Compare taking a family of four to a movie ($30 or more) to spending an evening playing the Wii. You only need to make that choice half a dozen times to break even.
I can also tell you that between Wii Sports, Super Mario Galaxy and Lego Star Wars, our family has easily recouped the total cost of our Wii setup. So the answer to how many games you need is as few as one, if the game is good enough.
But to go back to the original complaint with the Wii library, one of the reasons's there are so many bad games is because it's relatively cheap to develop and publish a title for the low-powered, widely-owned system. That means publishers are far more willing to take risks and green light more projects. But the flip side is also true: consumers can take a risk and buy unknown or marginal titles since the standard price of Wii games is $10 (or about an entertainment hour) cheaper than PS3 and 360 games. What's more, it takes a lot more to recoup the cost of the more expensive consoles (and potentially more expensive TVs and sound systems to go with them). In fairness, we probably need to shift the baseline from a regular movie ticket to an IMAX ticket ($3-$5 extra).