EDIT: No on the i3 (stupid sockets), but I'd still like to know what would be better.
It isn't only the 'stupid socket', LGA1155 CPUs have integrated memory controller while LGA775 uses north-bridge memory controller.
The IMC on new CPUs which cuts DRAM access latency by dozens of CPU cycles is one of the key reasons why LGA1155 CPUs perform significantly better than LGA775 ones.
Since LGA775 boards lack modern IOs and use DDR2 which is quite expensive today, I would have a hard time recommending sinking any money in it. If you cannot afford a platform upgrade, I would strongly recommend waiting until you can unless your current PC is unbearable.