I have had no heat issues with my thinner MBP.
With the cMBP, if I run a reasonable graphical load (say, Minecraft even), I get fan speeds up to 6kRPM within a minute or three, which is pretty loud. With my G53, it makes a much quieter fan noise under any load I've ever found for it. Probably because the fins alone on the outgoing vent for the heat sink are taller than the MBP.
So far, my MBP experiences have been:
2007ish (GeForce 8600): Famously prone to massive failures from overheating. It was slow but livable for me, and if I set games to throttle frame rates, it never actually failed badly for me. Sold it to a friend in 2010, and the 8600 died spectacularly with about one month left on AppleCare.
2010 (GeForce 330M): Marginally faster than the 8600 at video -- noticable, but nothing incredible. No obvious severe damage from heat, but it was a little crash-prone. Got iStat Menus, set it to keep the fans a bit faster, and it was stable but quite loud.
2011 (Radeon 6770M): Tolerable performance, not crashy, but fans ran up to 6k and stayed there under basically any load.
2012 (GeForce 650M): Decent performance, by far the best of the lot (I don't just mean "faster than the others", I mean "faster compared to other hardware on the market than the others"). Haven't tested the fan behavior much yet.
Okay, on the 2012, I just started up Minecraft. Windowed, smallish window. CPU temp reached 97 C almost immediately, fan is now ramping up. Fan speed is gradually increasing, CPU temp has hit 102 C. Hovering around 100 C, with fan speed continuing to gradually increase. So, on the bright side, it's not running nearly as loud as it did on the 2011, but it's running a LOT hotter; the 2011 would have had the fans to 6k before letting the CPU reach even 90 C. Multiple threads elsewhere say that this is bad -- the CPU should not be clearing 85 C. Fan speed up to 4480 and still slowly rising. ... Okay, another couple of minutes, now at 95 C and 5500 RPM fan speed. Note: The minecraft window isn't even visible, it's in another desktop space. (I love me some mission control.) Temperature sensors are, according to iStat Menus, "CPU Die - Digital" and "GPU Die - Analog". Ambient temperature is pretty low -- my office is in a slightly drafty basement, in Minnesota.
Okay, it's finally reached 6kRPM, and the temperature's down to 88. Definitely louder than my G53 gets under any load I've ever managed to put it under. Also, and this does matter, the noise is a higher pitch than the G53's fan noise, simply because it's faster-moving air through a smaller area; the G53 may well be moving just as much air, but it has a lot more space to move it through.
Went and researched other stuff a bit, came back and checked: 87 C, 6200 rpm, a little louder than it was before.
I tend to have a LOT more space available on my split SSD on Mac side than Windows side.
The point is, I don't even
have a Windows side, and I have the disk 88% full, having had the machine nearly a week. This is my primary working Mac. It has all my stuff on it. A bare games machine install for me would have ~70GB of games on top of Windows, give or take, so it would need >100GB of storage. So basically, I'd need a larger-than-512GB SSD to even
do a split, and this really does not appeal to me at all.
The Retina supposedly has better thermal management, which wouldn't surprise me, but it has other issues that prevent me from getting one (such as the lack of an option of upgrading the SSD...)
So for now, I'm sticking with a dedicated gaming laptop and leaving the MBP to run only relatively low-powered games, because it's just not competitive in terms of fan noise and cooling with the machines that are built specifically to dissipate the heat they produce. Not to mention the PC having 2x the VRAM.