You can argue what happens in round three isn't per the rules, but the spell specifically requires 'unreasonable commands' to be refused.
Round 3: 1st genie is killed by party wizard orders 2nd genie to give 3rd ability score increase 2nd genie refuses because it has become an unreasonable command, since he now has every reason to believe he will be dead after the 2nd wish is granted Round 2: 1st genie grants 2nd ability score increase Round 1: 1st genie grants 1st ability score increase Both genies are asked to give +3 inherit ability score increases when requested (note the timing has to be part of the agreement, even if it's simple 'On my command'), and both are successfully compelled Setup: Both genies are bound, with dimensional lock in place.
Since you need at least two genies to get to +5, how would you arrange it so that both of the genies died and you still get your +5? Since by the rules, the wishes must be granted in consecutive rounds, the best scenario I see here is:
