There is no single "best" aircraft, it's all largely a matter of taste and preference. A very personal selection:
GA:
- Cessna 172p
- Piper PA-28
- Seneca II (twin engine)
Short haul turboprop:
- Beech 1900d
- Q400
Short haul jets:
- A320 (the IDX version)
- 737
Long haul:
- 777
Bonus (won't fit any of these categories, but somewhat similar, and too nice to not mention):
- DHC-6
- DC-3