Good thing I saw this thread. I was just wandering where to suggest the Might and Magic pack [http://store.steampowered.com/sub/12368/]. for 20 quid (or 30$) you get all of Heroes 5, Heroes 6, Clash of Heroes and, well, Dark Messiah, but at least you get the others cheaper. I would have bought it, if I didn't own every single game there. I'll do a mini break down, if you decide to go for only some of them (or none):
Heroes 5 is a really nice game, especially with the expansions. I really recommend it. if you liked H3, this one would both be easy to pick up and improve on some of the aspects of it. If you haven't played H3, it's still a nice game to get you into the Heroes series. Overall I'm very pleased with that game.
Heroes 6 is...well different. You'll either like it or hate it, because it's different to the previous ones. I like it myself - it tries to change things, and although it takes some steps back, it manages to break out of the stagnation in the Heroes franchise. At any rate, there is a demo if you wish to give it a try and decide before buying.
Clash of Heroes is like Baby's First Heroes meets Bejeweled. And I like it - it's not much but it doesn't cost much, either. If you want something where you can just lay back and play without much thinking, it's good. And I've had really enjoyable multiplayer matches, too. By the way, if you're buying it, pick up the DLC for it - for 50p it unlocks more multiplayer heroes to choose and the heroes are nice, too.
Dark Messiah - I don't really like the game. I mean, it's nothing much, rathert than "it's bad". It's kind of cool to play it for a while but it gets boring as it goes on. And playing a pure mage sucks hard in the beginning, as far as I remember. Pick it up with the pack, but otherwise, only if you're really into M&M. Oh, but it does do first person melee combat OK and there is a multiplayer I haven't actually tried, so there may be some reason to get it.
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Other than the M&M pack, I'd suggest to look out for Magicka, in case it's reduced further. It's an awesomely fun game and I really enjoyed it.