I haven't played Magicka (I have it in my account but the tutorial is the extent of my travels within the game) but for the bolded part, while I cannot comment on Isaac's controller support if I were to choose between it and Blood Dragon I would go for Isaac if based purely on the quality of the game. Now, make no mistake, both games are enjoyable and it will likely come down to your preferred type of game but I feel The Binding of Isaac (in addition to being cheaper) has much more longetivity. While Far Cry: Blood Dragon lasts, it is an extremely enjoyable experience with a great soundtrack, decent shooting (although I don't feel that it is enough to sustain the game following completion), good dialogue and a wide environment filled with some interesting missions. It is absolutely worth buying at the price and I wouldn't dissuade somebody with an interest solely in it to buy it. However, following the completion of the missions, I feel it's pretty much done and the fun that was to be had, has been had. Make no mistake, seven hours (which is what I'd say it roughly takes to complete it, add or subtract an hour or two depending on exploration and pace) of an enjoyable game for a low price is excellent but when between it and the Binding of Isaac I'd have to give the advantage to the latter. The game is simple, as you'd expect (the simplicity of the gameplay may harm it for some so if it's a dealbreaker that's understandable), but the huge array of items and the randomness of the game make it very addicting with enough content to last a considerable length of time. Whereas with Far Cry once you're finished the game, that's pretty much it, Isaac is an extremely replayable game, the randomness keeping each run fresh even after unlocking the large amount of content. There's a touch of dark humour in the game if it appeals to you and the soundtrack is quite excellent. I bought it on what was more or less a whim after seeing somebody on this site rave about it and I was very surprised that it ended up my most played game (54 hours logged, about 200 more hours in offline mode); not through long marathon playthroughs but by turning it on every now-and-then and playing through with the intent on finishing it (if I do, I do, if I don't I turn it off; it's pretty much just to occupy some time).
It's certainly not a game for everyone and I've been led to believe the controller support is quite poor so if that's a dealbreaker Far Cry: Blood Dragon is absolutely worth getting but I would still keep The Binding of Isaac in mind.
EDIT: Also, it's worth noting that I played it from the beginning with Wrath of the Lamb which, to my knowledge, adds a considerable number of items so I cannot compare what the base game is like on its own to what it is like following Wrath of the Lamb's installation.