I think the best way to do this is to compare the good conventions/features of the Jones films with the bad conventions/features. To be fair, I will include the good aspects of the Crystal Skull and the bad parts of the first three films as well.

Good: Unrealistic, yet almost plausible action

Examples: being drug behind a truck by a whip (Raiders-R), downing enemy planes with a flock of birds (Last Crusade-LC), cutting a rope bridge while standing on it (Temple of Doom-TOD), escaping an atomic blast inside a lead-lined refridgerator (Crystal Skull-CS).

Bad: Unrealistic, totally rediculous and dumb action for a cheap comedic effect.

Examples: lead-lined refridgerator thrown thousands of yards through the air with Jones inside (CS).

Good: villans that are somewhat developed and complex

Examples: Belloch (R), Dr. Schneider (LC)

Bad: shallow, cartoon-like villans

Examples: thuggee preist (TOD), Russian Lady (CS)

Good: side characters that move the film forward by contributing to the plot.

Examples: German guy with burned hand (R), Sala (R), Marcus (LC)

Bad: side characters that are a gimmick to move the film forward by foregoing plot.

Examples: fat greedy guy (CS), pocessed idiot professor friend (CS)

Good: attractive, empowered female who complicates the hero's choice of actions.

Example: Marion (R), Dr. Schneider (LC)

Bad: annoying stereotypical female who does little to challenge the hero's decisions.

Example: Lounge Singer (TOD), Russian Lady (CS)

Good: compulsory giant cliff used to kill off enemies.

Examples: on the road to Cairo (R), the canyon of the cresent moon (LC)

Bad: compulsory giant cliff used to show that forces of gravity can have no ill effect on god-like protagonists.

Example: mountains of northeast India (TOD), Amazon river valley x3 (CS)

Good: film opens in medias res with an independent adventure that gets the viewer warmed up for more and introduces/develops key characters.

Example: golden idol in Nicaragua (R), ashes of Chinese emporer (TOD), cross of Coronado (LC)

Bad: no independent opening adventure and no subtle preliminary character development.

Example: area 54 (CS)

Good: main character is a rough and tumble adventurer driven by intellectual curiosity and the desire for fame and fortune, which is complicated by personal connections and a reluctant devotion to basic morals and values.

Example: Inidana Jones (R), Inidana Jones (TOD), Inidana Jones (LC)

Bad: main character is a patriotic, x-spy threatened by red-bating, who is driven by the need to be the savior of his friends who have been thrust onto the front lines of the cold war.

Example: Indiana Jones (CS)