I say Niang for sure. Cyclones wrote to him and he wrote back. The love that he has given Ames from the time he stepped foot on campus and still to this day are hard to beat. The dude gave it his all, embraced us fans and he'll definitely be an all time favorite. This is why he's still my CF thumbnail. Fred is up there, but the thing with him is yeah he was well liked, he came back and resurrected the program, but did decide to leave. While I don't hold that against him and understand career paths, it happened so Georges is the icon in my book.
There was something about those guys - Niang, Monte, Naz who just represented the team with class and did everything they could with and for fans and the school. It was a fun time and so enjoyable to watch and experience. Brock, Lazard and DM is kind of up there for football the way they gave it their all, brought the team back, and still carry the ISU torch to this day in the NFL. They're just really good dudes who seem to love life and have fun while not forgetting Ames in the process. Had Haliburton stayed longer and/or didn't get hurt I think based on his likeability and representing ISU, he'd be up there too. They just have a charisma about them that bring a positive attitude to others and are well liked.