It depends which airline is available for a specific destination, some Airlines don't fly specific countries. Out of the British Airways, South African Airways, China Airlines, Emirates, Singapore Airlines and Cathay Pacific Airways I have been on I prefer Singapore Airlines.
As for best Airlines changes every year.
Air New Zealand wins 2017 Airline of the Year
AirlineRatings.com's top 10 airlines for 2017
1. Air New Zealand
2. Qantas
3. Singapore Airlines
4. Cathay Pacific (Hong Kong)
5. Virgin Atlantic/Virgin Australia
6. British Airways
7. Etihad Airways (UAE)
8. All Nippon Airways (Japan)
9. Eva Air (Taiwan)
10. Lufthansa (Germany)
Skytrax World Airline Awards The World's Top 12 Airlines in 2017
Emirates wins 2017 Skytrax Airline of the Year
1. Emirates
2. Qatar Airways
3. Singapore Airlines
4. Cathay Pacific (Hong Kong)
5. ANAs (Japan)
6. Etihad Airways (UAE)
7. Turkish Airlines
8. EVA Air (Taiwan)
9. Qantas Airways
10. Lufthansa (Germany)
11. Garuda Indonesia
12. Hainan Airlines
Safest Airline in 2016 according to Airlineratings released in early 2017.
1. Qantas
2. Air New Zealand
3. Alaska Airlines
4. All Nippon Airlines (ANA) (Japan)
5. American Airlines
6. Cathay Pacific Airways (Hong Kong)
7. Emirates (UAE)
8. Etihad Airways (UAE)
9. EVA Air (Taiwan)
10. Finnair
11. Hawaiian Airlines
12. Japan Airlines
Safest Airline 2016 according to Jet Airliner Crash Data Evaluation Centre released in early 2017
1. Cathay Pacific Airways (Hong Kong)
2. Air New Zealand
3. Hainan Airlines
4. Qatar Airways
5. KLM (Netherlands)
6. EVA Air (Taiwan)
7. Emirates (UAE)
8. Etihad Airways (UAE)
9. Quantas
10. Japan Airlines
11. All Nippon Airlines (ANA) (Japan)
12. Lufthansa (Germany)