I'm fairly certain World of Warcraft has that by a fair amount.
WoW costs 14 dollars/month. Let's say 10 million pay for it each month. That's 140 million a month in revenue. That is (roughly) the same as selling 3 million for your average game. Over the course of a year, it's around 1.6 billion in revenue, so I'd say it's safe to assume that from monthly fees alone it's at over 3 billion in revenue so far in its life. Then there's the original game and the expansions, which I assume have sold around 20M in total (perhaps more). They don't go at full price, do they? It's more ala 30 dollars each, which would lead to another 600M revenue.
All in all: WoW is likely to be at around 4 billion in revenue. Now, this isn't all profits, but that's the same as selling 80 million 50 dollar games. Now, keeping WoW up and running with the servers, as well as creating updates/expansion is probably far, far more expensive than your average game. Still, I can't imagine this coming close to a billion. That's just guesstimates though.
I doubt Wii Fit is second. The balance board isn't free, so despite its high revenue, it's not making that much profits. Its profits pr game is probably similar to your average 50 dollar game. Wii Fit may become second, but it's not there yet. It does have the advantage that while most games have a price drop, Wii Fit hasn't had one. Its current profit is likely to be around a billion.
For second, I'm thinking the Sims. Well, if you count expansions that is. The franchise has sold 100M, and the Sims 1 was larger than the Sims 2 (I'm guessing a 60-40 split, but I may be wrong). The expansions don't cost all that much, but with an average price of 40 dollars each, that's 1.8 billion in revenue. The Sims' budget was probably incredibly small, but advertising and such still cost a fair bit. Even though of that, its' total cost is unlikely to be higher than 150 million. Then there's the question of whether or not you should count inflation, which would put this at a good 30% higher in profits.
Tetris is far, far away. Handheld games tend to cost 30 dollars, and as such they sell for far less. No handheld game holds a chance here.
So, off the top of my head;
1. World of Warcraft at 2.5-3 billion profit.
2. The Sims at around 1.5 billion, or 2 billion with inflation, profit.
3. Wii Fit at around 1 billion profit.
