Touche. But I don't have to actually be face to face with them here! 
I think the argument here is not whether or not ME2 advanced the Reaper plot (which it easily could have if Harbinger played a significant role in ME3's plot), but whether ME2 needed to advance the Reaper plot to be considered "connected" to the series. My view is that technically, Mass Effect's plot is to stop the Reapers from destroying the galaxy. That second part is necessary because I think that ME2 is about answering the question "what galaxy?" Obviously ours, but who's in it? Why do I care about them? Why won't this fight be as simple as getting a big gun and telling everyone to work together?
Mass Effect isn't simply "the quest to find that thing that'll kill the Reapers," it's a story about unifying the galaxy against the Reaper threat, and ME2 adds complications to achieving that unity. In my opinion, that's pretty vital thing to establish. I still think ME2 could have done a better job expanding on (or even resolving) the political corruption in the Citadel and Terminus systems and conflict with the mercenary groups, but it has enough important additions to justify its existence within the overarching plot.
You're right but what you're talking about is all the side stuff, and I agree that stuff was great. ME2's entire value was in developing the characters. ME2 certainly shifted the series from plot focused to character focused, like Star Wars is. However, that has nothing to do with the main plot. Killing Shepard, destroying the Normandy, expanding Cerberus, and introducing the Collectors had no value whatsoever.
Secondly, everything was bound to the individuals. The parts of the game that had to do with the Genophage weren't about the Salarians or even Krogan generally, they were about Mordin. The drama in curing it in ME3 is bound in Mordin and Wrex and, as much as I like Padok Wiks, the entire thing is diminished without those two characters. The same is true of the Rannoch arc with Tali and Legion.
Well in my opinoin it did so again I think your confusing what facts and opinions are
No, you're the one doing that. It objectively did not progress the series plot. Please tell me how it did. Your enjoyment of it is what is subjective opinion. I also enjoyed it but that had nothing to do with the main plot. It had to do with gameplay and the excellent characters.
Exactly as in my opinion the reaper plot is advanced as in terms of the story is they changed tactics as they realised that using the geth was no longer going to work so instead they activated the Collectors and got them to start working on attacking the smaller colonies and start building a reaper ready for their arrival
This is just wrong. The Collectors were building the next Reaper, not doing anything to bring the Reapers back like Sovereign was with the Geth. It wasn't a change in tactics, though. It was something completely unrelated, unless you think they were going to deploy the Human Reaper to try Sovereign's plan again.
Not for the players they don't. You play your character. That's it. If your character dies as a result of his choices, that's a legitimate outcome.
The character might have failed, but the player didn't.
My favourite Warden in DAO was an abject coward who refused to learn useful combat skills. My goal in that playthrough was to see what would happen if I built a character like that. He died in Haven when Sten killed him. I call that a wholly successful playthrough.
I don't even understand how a player could fail in a roleplaying game.
That's just you creating your own game within the game. You're defining your own objectives. That's perfectly fine, but that's what it is. That doesn't make the actual game not a game.
I disagree. ME2 covers the the 3 main sub-arcs of the series: the Geth, the Genophage, and the Citadel council. Turians and asari are covered under Citadel politics and salarians are closely tied to the Genophage. Admittedly, ME2 should have covered Citadel politics more deeply, but Mass Effect never needed to examine each culture separately. Unlike DA:O, the sub-arcs involve multiple cultures interacting with each other rather than individual cultures dealing with their own problems.
I liked how ME2 tore all our accomplishments to shreds because it reminds me of Empire Strikes Back. ME1 set us up with a fairly simple conflict that was bound to be solved by some plot contrivance (the only way to defeat a horde of god machines), and ME2 adds a host of more personal conflicts along the way. By the end of Mass Effect 2, you have a number of connections throughout the galaxy with high ranking officials and specialists as well as close relationship with Harbinger. Really, it's all ME3's fault for not leveraging that.
The Geth alone are not an arc so I assume you mean the entire Geth/Quarian conflict. Yes, that is developed but not along the main plot. The same is true for the Genophage. What happens with Citadel politics? You have one meeting with the Council. What exactly was developed regarding Turians and Asari?
Also, as I mentioned above, the Genophage and Quarian/Geth conflict are particularly focused on the characters, Mordin, Grunt, Talki, Legion, and Wrex. They are not focused on the species as a whole.
The difference between ME2 and The Empire Strikes Back is that the film does advance the main story. Star Wars is entirely focused on the characters, with the war against the Empire being the back drop for the character stories. ME2 shifts Mass Effect into a similar story. So the most important things in Empire are Luke training with Yoda and facing Vader. Luke develops and a major plot point is revealed. When does this happen in ME2? Where does Shepard change? What of value do we learn about our opponent? Shepard, and most of the other characters, are barely phased by Shepard's death and resurrection. There's just one line about it in ME3, a game too late.
What connections of value, other than Liara as Shadow Broker? Shepard met Aria but while she shows Shepard some respect, she doesn't really care about him/her.
End of ME1: The Reapers are coming to kill us all and we have no way to stop them.
End of ME2: The Reapers are coming to kill us all and we have no way to stop them. Also they are closer now.
ME 2 is arguably the best game in the series. ME3 had errors but doesn't every game in history? Always something for people to complain about. Always.
That may be but it certainly is not because of the plot.