It isn't good enough to have the best CTR or higest budget or clicks. You have to be willing to "risk" money to get the top spot.
You gotta want it.
For example we have a lot of "blue" ads where our max CPC bid is $2 even though we usually pay about .67
If we lower our bids to $1 we are still #1 but lose the blue spot (no one has it).
You gotta have a substantial bid.
"...the top position always has the lowest ROI."
I must agree with the lowest ROI post above, but also, must remember that lower ROI doesn't mean less total profits.
1000 sales at 150% ROI can be much more profitable than 100 sales at 300% ROI.
ROI is not the end all number, it's just one measurement in a sea of many.