The cards are not in standard any more as they are too old, and Emrakul is banned in EDH (although I'm not entirely sure why). But legacy and other formats? Completely fine. But not that powerful - There are legacy decks which can win technically before turn 1 starts. I have a deck that is built around this entire idea - Get out Emrakul and make it unkillable. Platinum angel is also out of standard due to age, but allowed in all other formats.
The problem with running MtG in the way you are here is that there is no mana to act as a limiting factor. The first turn I cast in an actual game would have needed 20 mana of any colour to pull off. That would take a long time to set up, or need multiple turns (as a side note, there are ways to gain infinite mana, infinite turns, infinite creatures AND infinite counterspells. All from the same deck. I've done it. These are also completely legal in most formats). As another aside, I have a deck which legally "cheats" Emrakul into the game very early on. I should make a thread to list the horrible, murderous card combos I have decks built around.
EDIT: As for countering this particular setup, I can think of several cards that would do it easily, with the lack of mana per turn restrictions xD