I would like to find out what other traders feel is the best singular statistic for evaluating performance? There is no "right" answer here, it is partially a subjective decision. I'll start with one approach I have found to be very useful:

- Take the annual Net Profit, including a reasonable baseline commission, and divide by the draw-down. The higher the number the better the system. Here is an example:

1) Net Profit = $141,000 over 3 years = $47,000 annual Net Profit. Included $8 round-trip commission.
2) Draw-down = $12,000 historically.

Performance = 47,000 / 12,000 = 3.92. A value above 2 is a good system, so this is an exceptionally good system.

Here is my reasoning:
1) Draw-down gives the overall risk better than anything else. It is where a system had its greatest streak of losses in a row. Using Monte Carlo simulations you find that above 90% of the time 2 X draw-down is the absolute worst case. Therefore risk is directly proportional to draw-down.
2) Annual net profit averages the years of backtesting into one number. So if a system has a broad deviation over years it is spread over the average net profit. (I also always make sure there are small deviations for annual net profit year over year).

This ratio provides a good single measure for reward vs. risk of a system.

I tend to use Profit/Loss ratio and Risk/Reward for short term evaluation, but pretty much what you said for long term.

Antisyzygy 

I tend to use Profit/Loss ratio and Risk/Reward for short term evaluation, but pretty much what you said for long term.

What is interesting is how the #1 issue for traders is figuring out if they are profitable and by how much, and yet less time is spent on this consideration than you would expect. I know when I started out I looked for profitable systems to trade, either my own, a hedge fund, a CTA, or an auto-trade system. I had few metrics to judge a good system from a bad one. It was like shooting darts at a dart board. It was not until I was profitable, or rather I can say I became profitable because I understood the metrics! Once I was armed with a gauge for both my own discretionary as well as system trading, I could see the frauds from the honest sellers of systems.