GTA V has lower minimum system requirements than Forza Horizon, but since you don't give us your current system specs, it's impossible for us to say.
GTA V Minimum System Requirements:
OS: Windows 8.1 64 Bit, Windows 8 64 Bit, Windows 7 64 Bit Service Pack 1, Windows Vista 64 Bit Service Pack 2* (*NVIDIA video card recommended if running Vista OS)
Processor: Intel Core 2 Quad CPU Q6600 @ 2.40GHz (4 CPUs) / AMD Phenom 9850 Quad-Core Processor (4 CPUs) @ 2.5GHz
Memory: 4GB
Video Card: NVIDIA 9800 GT 1GB / AMD HD 4870 1GB (DX 10, 10.1, 11)
Sound Card: 100% DirectX 10 compatible
HDD Space: 65GB
DVD Drive
Forza Horizon 4 Minimum System Requirements
OS: Windows 10 64-bit
Processor: Intel Core i3-4170...