Downloading ISOs for games you do not own is considered copyright infringement in most regions.
The GameCube version is a solid port of a classic. It’s slightly inferior to Xbox (better graphics) and PS2 (online mode) but still highly enjoyable. Ideal if you want a dedicated single-player racer on Nintendo hardware.
When searching for a "Need for Speed Underground 2 GameCube ISO link," safety is the priority. Many sites promising direct downloads are filled with intrusive ads or malware. Legal and Safety Guidelines