There's no such thing as a "Best" ball. There are too many balls and there are too many styles and there are too many oil patterns.

 

There are sets of the "right" ball for your delivery and release for varying amounts of oil and oil patterns. You should probably get together with one of the good pro shops in your area to let them analyze your style and understand what kind of conditions you bowl on. Talk to some of the higher average bowlers and get a consensus of which pro shops in your area "do the right thing", with respect to truly analyzing and recommending the proper balls for you. That includes watching you bowl and not recommending the most expensive ball they sell. (Many pro shops won't watch you and just try to sell you the strongest, most expensive  ball they have. That is NOT the "right thing"to do.)

 

Very good point(s)! As an analogy: it is much like a car: there is no "best" car. If you want to win a NASCAR race you probably do not want a Hummer, even though that type of car excels in its home turf. "Best" is very relative, and even if you take one car to two drivers, their driving style and setup will probably make the same car look and behave very differently, aven on the same track. Bowling balls are just as complicated - you need to make up your mind on which condition and for which purpose/reaction you want a ball. That's when one can make some vague suggestions what might be a good basis for an effective solution.

DizzyFugu - Reporting from Germany
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I think you missed the point the other posters were trying to get at.  OUR favorite balls may not be the best choice for your style or lane conditions that you face.  You would be better off talking to either the proshops in your area or to the higher average bowlers in your leagues or leagues in your bowling center.  At least they have probably seen you bowl or bowled on the conditions you have.
 

Five more responses than I thought this would get.