The Maximo Im-590s are currently the best all-arounders IMO. They offer the best combination of balanced sound, isolation, and comfort. The Soundmagic PL50s are extremely light, small, and comfortable. They also benefit hugely (in my experience) from aftermarket tips and have a much more laid-back sound with somewhat weaker bass. The NE-6's are the opposite - they are still good all-arounders but have a very strong bass response.
The Ai-M6 used to have really bad cables, but they have just been updated with a (reportedly) hugely improved cable. I have a feeling that with nicer cables they may become my new favourite budget earphones because they do sound incredible for the price - strong bass, huge detail, great extension. The Apple Dual-Drivers and RE2's are also very detailed headphones, but the bass is not a huge improvement on the Er6i, so you may want to skip them.
Lastly, the Radiopaq Jazz, which might be a bit of challenge to get your hands on, are extremely smooth and warm-sounding and offer the deepest bass of the bunch. I needed to use aftermarket foam tips to get good fit and isolation with them, though.