Andromeda - Where is everyone else?

None of those 4 options explain why we aren't seeing more races
1) whats preventing other species from interacting with this cluster?
2) The andromedans have had billions of years beyond the level of technology needed to make mass relays to require them. Its actually impossible for an entire galaxy of species, given a time scale of billions of years, to not have come up with something better than mass relays at some point without an impediment like the reaper cycles. And sure some people will say that civilisations collapse, but do you know what? Something as impotant as advanced intersteller travel wouldn't be just limited to a single race. The knowledge would have been coopted by other races or invented again.  Therefore, the likelihood of losing advanced FTL travel  and the ability to travel from one side of the galaxy to another would be astronomically slim to the point of impossibility because the knowledge would have changed how races interacted with each other in the galaxy and it was deemed extremely important.
It would be like saying that all the races of the milky way forgot how to undergo FTL travel simultaneously. Short of a massive galactic catastrophie, I don't see how thats possible. And even in a catastrophie, its still really unlikely given the number of races that must have had the technology.
3) too vague to be of value
4) Why?

There could be plenty of reasons. eg:

1. We're going to a single cluster, not flying across half the galaxy.
2. The Andromadeans have a different form of FTL tech which doesn't allow for mass relay-scale travel.
3. The Remnant were the dominant galactic force and ruled over the other species until... something.
4. There are more species and BW just wanted to keep them under wraps.

at least compare MEA with just ME1, comparing it with three games at once is unfair. 

And I mean vanilla ME1, before Batarian DLC

Clearly a faulty assumption.  Look at our reality.  We've had millions of years of the development of life here on Earth without Reapers and have yet to truly leave even this single planet or actually break the speed of light barrier.  The only species we really know of in our entire galaxy are those we find here on Earth... and the only one we really give credit for being sapient are humans.

Mass Effect's timeline starts in 2183... a mere 165 years into our future.  It's really, really doubtful that we will have developed a speedy way to get around our galaxy by even that time.  Why would you assume then that the Andromedans would have necessarily done so.  Furthermore, Andromeda is a younger galaxy than the Milky Way.

Bioware might just be taking a more realistic approach to the timeline of their development.... and a reasonable timeline was something that was seriously lacking in the MET right from the beginnings of ME1.

Well, humans have only been around 100,000 years and human civilisation has only been around 10,000 or so years.  I mean its not clearly a faulty assumption because your rationale is not logical. The universe was around for 10 billion+ years before earth was even created, let alone had life on it. Its quite possible humans are late to the game in the universe. Just because we can't do it doesn't negate the ample opportunity for other sapient life to do so, does it? What exactly is stopping them, if they had a lot more time than us, or are smarter than us?
Also when you say andromeda is younger than the milky way, that doesn't matter because all a galacy is, is a gravity well around which stars move around. The stars themselves still existed before galaxy formation. Our galaxy will collide with andromeda and form a new galaxy in the future, does that mean that sentient species in this new galaxy could only start when this new galaxy is formed? That doesn't make sense.

Life of earth developed long before humans came on the scene... but, so far, there is no solid evidence of any species that has left our planet in the past and no solid evidence of species that flit about the Milky Way either.  It's all a product, so far, of our imagination.  That's why they call this science FICTION.  What you're assuming about Andromeda makes no sense given the reality we know of our galaxy which has had the equally long ability to spawn sentient life as Andromeda.

You do realise that we've only looked at about 100 light years in our own galaxy and have used radio signals at pi*hydrogen to look for alien radio signals to find alien life, a frequency an alien race would not use to communicate. By your logic, it would be looking at the corner of a room, not seeing any humans and concluding that there is no sentient life on earth. The absence of evidence does not mean the evidence of absence. Mathematically it is not possible for humans to be the only sentient race in our galaxy. If you truly believe that then we can all go back to the dark ages were humans were 'special', the centre of the universe and gods creation. 

I didn't know mathematics already proved we're not alone in the galaxy. Please, enlighten us!! 

I suggest you look up the drake equation to enlighten yourself. Some of the variables are based on probabilities but since we are gathering more information on the universe, those probabilities are getting less and less. I believe I have heard a string theorist say they have a more modern mathematical equation these days but you have to look it up.

The Drake Equation does not say with certainty that there is other life out there. As you yourself said, it uses probability and probability by its very nature is not a certainty. 

I never said it said with certainty, but the probabilites are so infinitesimally small it approaches impossibility, like a line approaches a tangent.  I didn't realise poeple would start looking for an argument unless you wrote like a lawyer writing an legal document. 
Everything is based on probabilities, even global economics, that certainly doesn't mean its incorrect and can be dismissed.