If you mean in terms of the main quest, you've just started Sequence 9 of 12, although Sequences 11 and 12 are both pretty short. I'd say you're roughly 65% done, you've quite far through but you still have a long way to go before it ends.
''Snake from Metal Gear 2 owns everybody. Because he used an owl. To make a guard think it was night time. In the middle of the day. That's just hardcore''