GTA sales are incredible. No doubt about it. But the trend is that each new GTA has taken longer and longer to create. I just read one analyst talking about 2016 for the next GTA. What? Not gonna happen. At earliest, it will be 2018, and based on previous trends it will be 2020. If that sounds crazy, it shouldn't if you note how long it took to make GTAV. The reason it's such an amazing game is what it takes to create it, and consumer expectations keep rising.

Still, the valuation of the company is low. If we assume 5 years, then the way I value TTWO is roughly like this... 

2013 $2.75 (when you account for tax); 2014 $1.75; 2015 $1; 2016 $2 (RDR); 2017 $1; 2018 $3 (GTA)  ~~~~ averages out to $1.92

at impatient market valuation (10x EM), it's a $28 stock, but at ATVI valuation (20x EM) it's a $47 stock

Even the risk of GTA taking another couple years doesn't knock that valuation all that far. I get about $25 and $40. The market doesn't care to wait so long. That's why I think the bigger publishers need to either buy them out or it's gonna be a loooong wait.