I've still got a Shogi in the works, sitting at 90% complete on my PC, sparked by an idea from here. I also think the NPC items in Super Mario Kart project started as a suggestion here.
But, I think if the eventual successor to this thread were to start off with something along the lines of "all ideas are welcomed and encouraged, but this is not a request thread. Do not expect others to share your interests or follow through with them." then posters would be less likely to repost, wondering why no one's done their bidding.
In fact; if we were to dig through the 100 pages of this thread, make a list of links of projects started by suggestions here, and compare it to the number of ideas proposed, it could make a mighty fine OP.
That said, I enjoy reading this thread, even if the "insert x character into y game, convert x game into demake/port of y game, and alter extremely specific aspect of some RPG" do tend to bore the daylights out of me.