GTA VI will be massive, a reported 210 GB download size would make GTA VI by far the biggest mainline GTA game ever.
For comparison:
• GTA III: ~1.1 GB
• GTA Vice City: ~1.5 GB
• GTA San Andreas: ~4.2 GB
• GTA IV: 10+ GB
• GTA V: 17+ GB at launch / around 87 GB on PS5 today
• GTA VI: ~210 GB reported
That means the reported GTA VI size would be roughly 2.4× the current PS5 size of GTA V, and around 190× the original GTA III.