Learn English – “My wife and I have been living here since we have been married.” is the tense correct

It's been a long time since I went to Canada.

To me, the above sentence is ideal only in cases where there is only one visit to Canada. In that sense, it would be both a first and the last (most recent) visit. That said, it's a valid construction in a situation where multiple visits had occurred, but in these cases I’d argue for:

It's been a long time since I have been to Canada.

The way I figure it, the statement above has two main pieces of information:

1. I have been to Canada (at least once; possibly multiple times)

2. It has been a long time since then (since my last visit)

Broken down the same way, the first sentence has these two main pieces of information:

1. I went to Canada (most likely just once)
2. It's been a long time since then (since my one and only visit)

So it comes down to what you want to say. This might be the situation:

1. I went to Canada throughout my teens
2. It's been a long time since then

You could make an argument for either option in this case, but I maintain that the second sentence would more clearly indicate multiple visits.

The two are interchangeable if you intend a continuative^† reading: that you have lived in Europe for the two years leading to the present moment.

^okI have lived in Europe for two years, and will not leave until next year.
^okI have been living in Europe for two years, and will not leave until next year.

But if you intend an existential^† reading, signifying that you lived in Europe for two years on at least one occasion in the past, you cannot use the progressive construction:

^okI am widely travelled: I have lived in Europe for two years, in Brazil for nearly five, and in Singapore for three. BUT
^∗ I am widely travelled: I have been living in Europe for two years, in Brazil for nearly five, and in Singapore for three.

^†For a somewhat more detailed description of these distinct uses of the perfect, see What is the perfect, and how should I use it?, especially §3.2 Pragmatic meaning.

^∗ marks an utterance as unacceptable