If you are going to buy a new computer i suggest you built it and not buy a whole computer. because builting cost about 200$ less on average and that 200$ can go towards a very nice graphics card or Cpu.
If you are a Hardcore gamer
{
CPU : GET THIS
PSU : GET THIS
GPU : GET THIS
RAM : GET THIS
MB : GET THIS
Case: GET THIS CASE
HDD : GET THIS
CD Reader : GET THIS
The items i shown above cost : $888
If you get a premade computer with same stuff it will be about $1001 As shown Here
and tell him you wana have some fun building it with him spend some father and son time with him