Best sensor to measure light intensity in open room
Analog "Light Sensors" for cameras have been around for decades. 

But for best? you're too late for the low cost $1 Sensors from  Panasonic the AMS-302 Light Sensors which are now obsolete.   They worked great on 5V to 12V and you set the gain with a load resistor and they take care of UV, IR and optically filter IR silicon response to the centre 530 nm green eye response that gives us a flat RGB response.

Now there are other options for analog and digital at more cost.

Forget about LDR's unless this is a $1 toy with huge tolerances and poor accuracy is ok.  Silicon PD's from Sharp/Vishay, on the other  hand, are remarkably consistent but low level and need TIA gain.

But you may want to use IR for emitters and detectors for collision sensing.  Analog or digital IRDA types or Remote controllers with AGC to bounce keycodes to avoid error detection. --- For currency, they use UV LEDs, and colors.

Go here for options. 

https://www.newark.com/sensor-optical-light-sensor-technology?ICID=I-CT-TP-BROWSE-5