1. 'For' is the "correct" preposition to use here. You can use 'for' with 'a long time' in any context: past, present, future, simple or continuous, positive or negative. It's possible to replace 'for' with 'in' in only a few contexts, mainly with negatives and superlatives in the present perfect and past perfect, for example "It's the best meal I've had in a long time" or "He hadn't seen his family in a long time". Some people see this usage as colloquial/non-standard. If in doubt, use 'for' : 'for' is sure to be right, while 'in' is likely to be wrong. 2. The sentence is wrong. You can't have 'ever' and 'in a long time' in the same phrase. You can have one or the other, both not both. ''This is one of the best games I have ever played." = in my whole life ''This is one of the best games I have played in a long time.'' = "The last time I played such a good game was a long time ago." Choose whichever one of those sentences you like .

Thank you very much, guys!

In a long time is used more commonly in the UK, and for a long time is used more commonly in the USA

I used to play football for a long time before I hurt my knee. It will take a long time for the potatoes to finish cooking. I am going to Steven tomorrow, I haven't seen him in/for a long time. I think both can be used here. But for the future "for" is better. I won't be seeing Steven for a long time. You shouldn't use "in" here. I'm no teacher but I hope it helps a little :)

FIRST QUESTION: Both are Ok but in UK "in a long time" is less used SECOND QUESTION: Correct. "I haven't had such a good game for ages" is another way to say the same thing :)