I think Watchdogs has pretty normal and average open world indirect lighting - it looks to use the exact same techniques powering every open world game these days (probe grid).I guess it really does depend on the game. Ultimately, to make a game look 'more CGI', the lighting itself needs to be better, and perfect reflections can help but won't save a game such as Watchdogs with its mostly flat lighting.
For example, a game with very, very good baked lighting such as TLOU2 would probably benefit more from RT reflections than Watchdogs. At the same time, making TLOU2 look as good as it does but with an RT GI implementation - instead of baked - may be outside of the performance targets we will get this generation. We'll have to see!
Watchdogs just looks flat, regardless of the reflections!
Given the amount of glass and metals in london and how often it rains, I think the RT reflections help the games visuals quite a bit: