For everyday drinking or the proverbial "desert island", I'd take plain Tanqueray.

For overall drinkability in summertime drinks or when introducing somebody new to gin, I go with Beefeater.

Hendricks is good, but quirky; I have to be in the mood for it, and take its cucumber flavorings into account when mixing.

Bombay Sapphire is a crowdpleaser; smooth, "gin-y", and impresses people who are impressed by such things since they have spent a lot of money establishing a high end brand identity. I prefer it very cold and >35,000 feet.

Despite my love for regular tanq, I find Tanq 10 too sweet. I have friends that swear by the stuff though.

Top 3 gin drinks by my personal consumption:
Tanqueray on the rocks, dirty
Bloody Mary with Tanqueray
Sapphire and Tonic