Honestly it sounds more to me that it's an issue whereby your old laptop simply had insufficient cooling and hence overheated.
To be honest I rarely see cases of Macbooks overheating. Sure, lots of people here complain that their Macs are extremely hot, but this is because the aluminium acts as a conductor for heat and feels hotter compared to plastic. However I've rarely seen cases here whereby Macbooks overheat and end up downclocking or shutting down to protect it, but I hear this more often on other brands of laptops.
Also, I'll just like to let you know that I have a Macbook Pro with an Nvidia 8600M GT. I've gamed thousands of hours (over 3000 easily) and it has never once downclocked itself or shut itself down because it became too hot. 4.5 years later it's still going on strong with no issues. Heck, I used to even overclock my GPU by as much as 30 - 45% (470/635 stock clocks, OCed to 600/900) for a year and it didn't run into any problems.