Yes, it took the Empire months to finish the Death Star however that's just one of many factions in Star Wars, Don't compare the Empire to the Forerunners when we are talking about ALL of SW Legends vs ALL of Halo my dude.
It's because the Death Star took months to build. I'm just saying that while SW builds 1 Death Star is <number> months, the Forerunners could build 1 everyday, possibly many more.
Size DOES matter. The bigger the ship, the better the tech. That was the case with a CSO, that's the case with the Infinity and that's the case with the Mantle's Approach. I have some knowledge about Legends, but I think it's pretty bare bones compared to die hard Legends fans. BIT, I prefer some things from it, like the aftermath of the Galactic Civil War or Luke's Jedi Order, as they sound way more believable and interesting. Legends FTW.
It's because the Forerunners were just that crazy. They only lost because their military, which was under control of a single AI, was turned against them. But overall, they're just too overwhelming even for Legends.
Also you're size does matter agreement is pretty weak, but you are right the bigger the most powerful however you still forget the bigger something is the greater the chances to hit and destroy it which is why I brought up real life examples to this debate.
The Forerunners are powerful yes, but their not unbeatable (I know about Mendicant Bias it's one of my favorite A.Is in Halo) and if the Flood can turn that AI against them I don't see why anything else in SW won't. Also the IE once again can build an unknown number of ships of droids not as big as the Forerunners however they can swarm the Forerunners in battle (like an enemy that made the Forerunners made the Halos in the first place), and that's just one empire in SW the Yuuzhan Vong are crazy my dude I want to say something about them, but it looks like they might be canon based on how the books are going right now, so all I'll say is it took almost everyone in Star Wars to work together and to put away all the bad blood just to have a chance to beat these guys.
Well, alongside the Forerunners, there's also Ancient Humanity, who were basically just as powerful as the Forerunners and only lost because they were fighting in two fronts. Actually, I believe that if they weren't fighting the Flood then the Humans would have won the war, even though there would likely be no war =P.
And of course, there's also the Precursors that defy all logic. They create, move and destroy Galaxies, they made the Star Roads, and can shape to any form they wish.
Oh, and just.... are you forgetting the Flood? The single most complicated parasite that destroyed both the Humans AND the Forerunners? The SW Galaxy would be a goldmine for the Flood.
Not really, and I'd give the same examples but I want to focus on the Mantle's Approach for this one. MAC rounds fired from ODPs were literally tickles to it. No effect whatsoever. And the Infinity's SMACs MIRACULOUSLY managed to penetrate it's shields, yet barely made any real damage that was repaired right away. And I'll remind you that MACs are ship killers. Now, yes, I'm comparing ODPs and the Infinity to a Forerunner WARship, but it's to give out an example of "the bigger, the badder".
And is there anything in the SW Universe, both Cannon and Legends, that has anything remotely close to the Flood? I can't remember a thing, and I have knowledge of some zombie-type creatures in SW.
Yes, the Yuzhan Vong is crazy, and it required both the Empire and Rebels to unite... but so was the Flood, even crazier actually. But alongside the Forerunners, there's Ancient Humanity. 2 Forerunner factions, basically. I won't include both the Precursors or the Flood in here. Just these two would be, maybe, more than enough.