While the title tells you most of what you need to know. I'll add in that I've never played an F-Zero game before. I recently watched some vids of GX and I must admit I'm intrigued. But I've always had this preconceived notion that the F-Zero series tended to be fairly sparse. 

As an Extreme G lover, will I go crazy for GX? 

It's a great game and developed by the same team at Sega (yep it was developed by Sega) that made the great Daytona series on Dreamcast BUT be prepared as this is one HARD HARD game and it really is fast and quite possible one of the few games that really does live up to actually being fast when racing.

You almost feel you really are racing at 1500MPH.

You should get F-Zero GX no matter what you thing of Extreme G. F-Zero GX is WAAAAAAAAAAAAAAAY better and have more personallity than Extreme-G.

And is effin' hard too. But in a good way! (Until you throw your controller on the wall XD)

ive been wondering the same as i own extreme g for gc but i also have never played a f-zero and have been wondering this

If I knew there was an F-Zero Wii game coming in 2008 I'd just wait for that. But with Mario Kart on the way, it seems unlikely Nintendo would have a second racer coming out this year.

Fzero GX is IMHO a masterpiece, the best chapter in the serie so far.

F-Zero GX is 100 000 times better than Extreme-G .You will love it .I think its the best F-Zero game yet .

I haven't played GX, but I hear good things. F-zero X on N64 was absurdly awesome, and crazy fast, so if GX manages to hold up to X then yes, by all means get it.

Personal Note, the original F-zero on SNES was on of 3 games my dad got me with my SNES. Also got Super Mario world and Roger Clemens baseball. I loved F-zero almost as I loved Super Mario World as a kid. Such an awesome series.

Well I love F-Zero, but I never really got into Extreme G, so I don't know how it works the other way around...

I only played Extreme G 2 a couple of times though, because I don't own it myself. I own XG3 and don't like it, but from what I've heard it is far worse than the N64 games, so I might not have enough experience.

The special thing about F-Zero is that there are 30 racers and you usually start at position 30, and the game gives you the time of three laps to get to first place. Also, the tracks are usually very funny but also quite difficult, meaning that you will fall down a lot of times, and falling down means the race is over.

If you have the possibility, I would try F-Zero X for the N64 because that is the best part imo. It isn't too bad if you start with F-Zero GX though. Just keep in mind that the 2D games are quite different, you don't start at the last position and there aren't so many racers, but driving is far more difficult and requires more skills. Those games are also amazingly funny though.

Yes, you should get it. I have played the Extreme G games and F-Zero GX is more fun than those (although my friend and I would play Extreme G on the Gamecube for hours, with all the cheats plugged in. Killing the racers is fun!)