Theoretically you can get all except M&M9 and Crusaders. However, since opinions are different, to be careful:

Might & Magic Sixpack (for M&M3 and WOX; also test M&M6 quickly and if you like it, get also M&M7 and M&M8)
possibly Might & Magic VIII (for Arcomage)
Heroes of Might & Magic 2 Gold
Heroes of Might & Magic 3 Complete
Heroes Chronicles: All Chapters
possibly Heroes of Might & Magic 4 Complete

Id recommend HOMM3 and HOMM4. Both are great, and totally different turn based strategy titles.

Homm Chronicles I'd recommend only if you're a fan of homm3.

From might and magic titles, just like the fella above me said - M&M Sixpack and/or M&M VIII

If you're shopping just for two games, it would probably make sense to get one RPG and one strategy/rpg.

For the former, I'd go with M&M 6-pack, or if you're into more modern graphics M&M 7or 8. 6-pack might be a better deal still, since M&M 6 is similar to 7, but you get 1-5 to boot.

For the latter, HOMM3 Complete is imho the pinnacle of HOMM series on offer in this sale.

The only one I've played through has been the Might & Magic 6-Pack. And I'd wholly recommend it. You're getting 6 games for like $5. That's the best deal.
Also, I like starting series from their beginning so if I was going to buy something from this sale other than the 6-Pack, I'd buy Heroes of Might and Magic 1.

Homm3 and Might and magic 1-6 would be my choice.

I just might get Homm2 and Homm3. I played both quite extensively back in the day.

The 6-pack has World of Xeen (Might & Magic 4-5), which, in my opinion, is the best part of the main Might & Magic series. You also get Might & Magic 1-3, 6 & Sword of Xeen, so that is a lot of games for your money! Consider it highly recommended.

As far as HoMM goes, all of the games, apart from 4, are quite similar. 1 has a lot less options than later games, and each game has some minor tweaks, but overall they are basically just versions of the same thing. If you have never played a HoMM game before, then I would recommend either starting with 2 or 3, and when you get to 4, have an open mind, it is very different (though not bad).

HOMM 3 is the best of them i think.

My recommendations :

Might and Magic 7 - Some will disagree but this one was IMO the best of the series. M&M 4 & 5 + 'Xeen' was great for it's time but can be a chore to get through these days unless you are just blinded by nostalgia. M&M 6 was a good reboot of the franchise but it's dungeons are long and often boring and the character creation and development pales in comparison to that of M&M 7(M&M 7 at least had a few different races to play, a few extra classes, a better skill system and the 'Arcomage' mini game which is worth the price of admission by itself!).

Heroes of Might and Magic 2 and 3 - Heroes 2 had outstanding 2D graphics with a bright palette, better music and in some ways better balance. Heroes 3 had the brilliant feature of both 'Might' and 'Magic' hero classes for each faction/town type(so instead of just a "Sorceress" as the 'woodlands/nature' hero, you had "Rangers"(might) and "Druids"(magic) for example) and also the random map generator(which made the game infinitely re-playable), lots of new items(combo-artifacts FTW!), units(probably 4 or 5 X as many as heroes 2). It suffered from some design flaws with the magic system(very many spells are completely worthless and no sane player would ever use them) and some of the names of creature upgrades and such as well as the horrible "Conflux" town/faction that was forced on us and rushed out the door due to a bunch of teenagers at the old Astral Wizard site complaining about the Warhammer 40k-ish "Forge" town that was planned).

Heroes 3 also had the 'wait' button which is a HUGE improvement over Heroes 2 in how combats play out.

Might and Magic 1-6 bundle - I would recommend this because A) you get 7 or 8 games for one low price and at least 2-3(most would say more I am sure) very good if not great games. None are as good as M&M 7 IMO but they are still well worth the price.

I am something of a completist so I picked up their Heroes IV bundle as well as their new Heroes V bundle(with the free "Assassin's Creed" which I have no interest in playing) but the only one of these I can really recommend someone else pay for and play is the Heroes of M&M V: Tribes of the East" game(included with the Heroes V bundle). Even with all the fixes and such for Heroes IV it is kind of lackluster compared to the other Heroes games.
Heroes Chronicles is something you will only want if you played through all the Heroes 3 campaigns and really want more of THAT. The Chronicles campaigns are well done for the most part but they are kind of a mixed bag. Many of the scenarios(most of them as far as I remember) are very small maps and if you will eventually be forced to play a campaign with a faction you don't like(for me it is the "Fortress" town/faction). Might and Magic 7(VII) had arcomage. M&M VIII had crappy 'races as classes' nonsense.

I disagree. I played through WoX for the very first time last year, and I loved it. And grid-based CRPGs were before my time, so it was not nostalgia that made me love the game.

My personal recommendation is Heroes of Might and Magic 3, and Heroes of Might and Magic 2. Just listen to this HoMM 3 track. It'll bedazzle youuu! ...hopefully.

To go into more detail, Heroes of Might and Magic 3 is definitely in my top 3 favorite games of all time, and it might just take the top spot (it's very hazy in my lists, the order of things is hard to discern). It's very possible that I've played it more than any other game ever, but I still return to it every now and then. The music is fantastic, and so is the gameplay. I enjoy myself even if matches turn into a chaotic dance with everyone teleporting everywhere with their massive armies and stealing your stuff while you're stealing theirs, all while everyone's avoiding combat with everyone because even the winner's army would be critically weakened. If it reaches that point, everyone who messes up or loses a fight loses the war (unless all of a sudden 4000 mighty gorgons join their cause in a random lucky event. oh man, that game took a while :p ). The game has hotseat multiplayer, campaigns, loads of maps and a random map generator (which sadly can make unbeatable maps, but it's rare, I've only come across two).

I recommend HoMM 2, because I prefer strategy games over RPGs, and HoMM 2 has some absolutely amazing music. The gameplay is good as well.

From a nostalgic point of view: HOMM2 and HOMM3. HOMM3 is superior to HOMM2 in every way, but I remember HOMM2 being soooo good back in the day, and I still think it's great, it's just that HOMM3 is better. HOMM4 is also very good, but some people don't share that opinion. It seems one either loves it or hates it. I think it's definitely up there as one of the best HOMMs.

If I had to put these three games in order from best to worst, I would say HOMM3 > HOMM4 > HOMM2. However, HOMM2 is still very dear to me, and if I had to, I would still choose it over HOMM4 if I could pick just two. So... it all depends if you have any previous connections to the HOMM-series. HOMM3 is a given though; no matter what other game you choose next, you should pick up HOMM3 above else.

Bear in mind my knowledge of the Might and Magic games is strictly restricted to HOMM only.

Well don't forget Heroes of Might and Magic V - you'll currently get free Assassin's Creed with it (albeit for 19 bucks, so it's like you bought 2 gog games :D), and I consider fifth part with expansion packs to be the best HoMaM game out there. It's got very interesting and varied skill system, it's far more balanced than past iterations, and it's got really, really lenghty games. Yes, that can be both good and bad.

I've played through the Might and Magic sixpack and Might and Magic 7, both were great.