Criteria for a fair trade?

I'd say first most important part about trade is desirability - who cares if you have AAA game when nobody wants is (Batman: Arkham Knights comes to mind - such poor port lots of Nvidia codes went down with price rather highly due to lack of demand).
After that, there comes sale prices - if it was sold on Steam with -75%, people won't really want to pay more than 50% of normal price.
And then comes bundled status, as that means game was sold with even bigger discount on one hand, while also was bought in large supply on the other hand.

As for the games asked: I really have no idea, as I have no knowledge about them.

I think (not sure; no source at hand) that Larry and Rex have been bundled in low ($1) tiers, Broken Sword 5 only in higher ($4+) tiers, so BS5 should have more "value".

i think 'bundle status' and sale price are kinda one and the same... what is the lowest price the game has been sold at - how long ago - whats the current sale price - how many copies are out in the market - how desirable is it.

thats pretty much the way i think things through.

When trading bundle games I usually consider both bundle price and desirability (if the game wasn't bundled many times and isn't available in the bundle atm sometimes that means a bigger price). You should remember that you never have to accept an offer you are not sure about or you don't think it is fair - you can make a counter offer but of course it is always up to the person you are trading with if they'll accept it and see it as a fair offer. You can use IsThereAnyDeal to check if the game was bundled, which tier etc.

The minimum value of a game is determined by the cheapest way it was possible to legitimately obtain it (in the same way as the one you're trading, e.g. on Steam), whether it's judged by sale price or bundling. The maximum value is determined by the cheapest way it is possible to obtain it at the time of trading.
A fair trade will always set a price in-between these two values. Desirability on the buyer's part (and greed on the seller's part) pulls you higher, while ease-of-stock (large supply) lowers the price, for instance when traders stockpile bundle games to resell later, their prices inevitably remain low.

It's quite simply a supply & demand kind of deal. If a game has been bundled once, in a high tier, but no-one wants it, then it's worth less than a game that has been bundled multiple times, in low tiers, but that people want. Games that were bundled long ago will be worth more, as there is less supply of those than games that were bundled yesterday (demand will also be lower for the recent bundle, as those who wanted the game could easily have picked it up), and if it was in some obscure bundle, like the 5 games for $5 bundle, then that means that supply will be lower than if it was from a super popular one.

A fair trade is in the end a trade that left both parties happy. Both parts got what they thought was a fair price for the game.