The Core 2 Quad Q9650 is a great processor, still. The Core i3-4130 is just slightly better than it however. Both should perform great with games, where the i3 may have the upper-hand by a margin; although if the game you desire to play utilises Hyper Threading and more cores, the i3 would perform better due to HT, as the OS sees the Hyper Threads as additional cores.
To be honest, the Core 2 Quad is still viable, albeit begging to show it's age. The i3 you mentioned is slightly better than the C2Q, where i5's and i7's will run circles around the C2Q.
To note however, the C2Q requires a socket 775 motherboard (if your current motherboard is 775, and supports the C2Q, then there are no issues here), whereas the i3-4130 requires a socket 1150. If you're on socket 775, then upgrading to the C2Q would be great if you can get it cheap. Again if you're on socket 775, then for the latest generation of Intel processors, including the i3-4130, you'll need to purchase a new 1150 motherboard. Your old DDR2 RAM will not be compatible with the new motherboard either, so you'll need to purchase new RAM as well. You may also need to upgrade your drives (hard drives, disc drive etc.) from IDE to SATA, if you're not already on SATA.
If you decide to stick to your current board for longer, upgrading to the Q9650 is a great choice; however after that, if you want to upgrade further, you'll need a new motherboard or a new build all together. Whereas if you go to socket 1150, you'll be able to upgrade the i3 later to i5 or i7.
All the best.