Mid ranged or better tablet formulations like Cascade Complete or Finish All In One seem to work better than gel based products. Powder based tablets also seem to cause less buildup in the dishwasher spray arms, screens, and tub (particularly noticeable if yours is a stainless steel tub). Regular powder detergents are hard to find, and if you can find them they're usually a lower end, simple formulation that doesn't clean as well as tablets. If you look at the ingredient disclosures online, the tablets usually have more active cleaning ingredients than powder or gel.
Also, enzyme based detergents seem to outperform chlorine bleach based detergents ever since the phosphate free detergent started to hit the market.
If you have hard water, adding phosphates as a booster may still be needed... but for most people the tablets seem to work fine.