If you want the classic Tomb Raider experience, I strongly suggest to stick to 1, 2 and 3. This two however... I have mixed feelings about them.
A lot of people give too much praise to TR4 for being return to the roots, set entirely on Egypt, and about nothing but exploring ancient tombs. While that's true and good, for me, it doesn't feel like the originals at all. You don't get the Croft Manor this time, which served as tutorial level, and also as a place to mess around. The satisfaction of beating a level is gone, with level being more like liked areas, so no statistics and the end of each one. Some of this areas are massive, meaning a lot of backtracking if you don't know where to go first. It's just impossible to beat the game without a guide, let alone finding all of the secrets, speaking of which... you don't know how many are per level, so you will only know if you found them all at the end of the entire game, and your reward for finding all of them is.... NOTHING, NADA. Given how impossible it is to this, they should've at least give you and extra level.
As for Chronicles, again, no Croft Manor, but at least this time the turorial is a section of the first level, with explanations in real time without interrupting you, and you can skip it entirely if you want. Also, no statistics at the end of each level, but at least can know how many secrets are if you found at least one, and there is a reward for finding them all. Its also more straight forward, never requiring to backtrack too much if you realize you are missing something. Each campaigns occur in different parts of the world giving some nice variety in scenarios. The first section feels absolutely like a classic tomb raider game, where the rest dives more into TR2 and TR3 territory, with the last level taken out of a James Bond Movie.
All in all, a good package, but you should definetly play the first 3 first, and wait for a sale on this one.