Which philosophy do you think is the most true, and why?

To me, what matters in philosophy and philosophical systems isn't being true or untrue or being more true rather than less true, what matters is how they relate to life as it is understood personally, that is, to your life. Philosophy is usually characterized as being an impractical activity and as serving no practical purpose, but this hides the fact that, since its very inception, philosophy appeared to serve the individual in its quest to make sense of the world, to provide a firm ground upon which to erect all aspects of our spiritual life. It's the certainty (even if this certainty is just the certainty of not being certain) that gives us strength in our practical life and peace of mind. In this sense, philosophy serves to satisfy a need of the greatest importance. Obviously, it helps if the system or teaching is convincing and appears to be true, but that's secondary. After all, what may seem true to someone may not seem so to someone else.

Now, as for answering the question, in my time studying philosophy I've found no philosophy more truthful to me (and I mean truthful in the deep sense of resonating with me, and not just being true in a supposedly absolute way or in a logically demonstrable way) than the philosophy of the ancient Greeks. Modern philosophy just doesn't have the same practical and ethically appliable aspect that ancient philosophy had. It's a mostly sterile philosophy, one that's supposed to be taught at academia rather than to be lived.