I would say a 2002 would be the most fun choice. I bought mine when I was 18 and all the chicks digg it(still do), and it is THE BEST "drive in car" if you know that i mean. :=):
But there are some drawbacks, its a bit heavy on fuel. I get about 10km/L if I drive conservatively, although I doesn't happen often 'cause a 2002 is just too much fun. You could swap in an M42 for easy/reliable/economic power but to me the cost outweighs the gains. The 2002 also has good tuning potential, and it handles great stock and even better with a few bolt on mods. It can even hold its own on a track against new BMW's if set up well. Parts are relatively easily found but can get expensive through a BMW dealer, but the M10 engine is almost bullet-proof, so if you find a good one it will last you a long time.
But your biggest problem might be finding one in a decent condition, and don't buy a "modded" one for your first car, you will only run into trouble. I searched for a 2002 for 2 years before I found one that was in a good condition. So finding one is hard, but look in junkmail/gumtree/autotrader. They do come up for sale every now and then.
I would say my second vote would be an E30, still relatively light and fun to chuck around, I actually prefer the 320i to the bigger 6 cylinders as you have a crisper turn in and less understeer with the lighter engine, and it is easy enough to move the back around with 320i. I also prefer stock tires and wheels(if you don't mod the engine) as the angle can be adjusted mid corner with a bit of practice. But then again, I suspect I am in the minority in this matter.
I would recommend getting a 4 cylinder car first time, it is cheaper to repair(if needed) and still loads of fun.
Some inspiration:
Regards
Jacques
This is the best car review I have ever read. Written by the late David E. Davis from Car and Driver. Read it, you will enjoy it.
C&D BMW 2002 Review
Regards
Jacques