It's been a long time since I've played a game that didn't push past two cores. Which games are you playing that don't? That's not to say the Q6600 would be better. It's clocked much lower and has a much lower IPC but a much newer dual core outperforming the first consumer quad core Intel ever released doesn't equate to games not pushing past two cores.
The venerable Unreal Engine 3 powered a whole lot of games last gen, and it was predominantly dual threaded at least in earlier versions (Interesting blast from the past article about it here). I can't speak as knowledgeably about other engines although I suspect prior to the PS4/XB1 games were still very much dependent on one or two fast threads. Personally I had to drag an E8500/GTX260 combo all the way into 2015 due to severe lack of funds for an upgrade and it done remarkably well at the likes of Bioshock Infinite and Far Cry 2/3. Never tried anything more modern like Witcher 3 since I knew it'd be a bloodbath for such an old system - no doubt that even the fastest dual core nowadays just won't cut it at properly threaded modern games nevermind older dual cores.
IIRC the Unity engine was also entirely dependent on a single thread until fairly recently and that also powers a whole lot of games. Gamebryo (Fallout 3/Oblivion/Skyrim etc) also has problems with multithreading although frankly that engine is such an overall janky mess I don't think it's really relevant.