Games won’t run any faster because you have a 10,000RPM HDD, they may load slightly faster but Seagates new 7200,10 series with perpendicular recording have great access times and they don’t spin so fast. If you absolutely have to have the fastest then go with that HDD otherwise it’s a lot of money for not a lot of space.
The 74GB isn’t as impressive these days, but the 150GB isn’t bad and offers improvements.
And yes, it won’t make your games faster. It will cut down on loading times, which will add to a smoother gaming experience, assuming you’re not held back by other areas (like amount of RAM or the video card in use).