Most reliable used simple/basic vehicle?
Out of the 30-something cars I owned in over a decade here are my favorites.
OBS GMT400. 4.3L, TH400, 34gal tank. 'Nuff said.
These Hyundai Accents are plentiful, often around $2000-$3000 with 100-150k miles. Fun, need nothing extra. Fuel, oil, tires, and a easiest timing belt job once every 90k miles.
It's basically a Corolla Hatchback. Your biggest issue will be replacing the odometer when it stops at 299,999 miles. I sold this one at 280k miles.
Second generation Pontiac Vibes are also fun. The optional bigger 2.4L is a nice bonus. Quick enough, and 32MPG.
Here is a close cousin of the Pontiac Vibe, Toyota Matrix, and Toyota Corolla: the Scion xB. Amazing car honestly. This was my first one, killed by 5AM

deer.
Loved the xB so much that now have another one, pushing 230k trouble free miles. VRP 5W-30 completely cured oil consumption on this 2.4L.
These FIATs are very underrated. 1.4T and a six-speed manual. Fun, yet I easily achieved 43MPG on long trips. Europe has these engines in everything, and with timely timing belt replacements these are know as Million Kilometer engines. That's over 600k miles in McDonald's units.
First gen CRVs are a hoot with the 5-speed and AWD. When I had All Terrains on it - it was tons of fun on sand, mud, snow, ice. Not a rock crawler obviously. More for rally-inspired driving.
Infiniti EX35, love this car. Recently bought it for $3200, and it needs nothing at 150k miles. It's a hoot with a boot, thanks to the VQ35 engine.
This was also cheap and reliable. I had my fun with it, sold it, and still see it often around town. The new owner isn't so great about maintenance though, so now it's burning oil, judging by the blue smoke clouds behind it... Sad

I loved this swagger wagon spaceship. Fully reclined seats almost formed a bed, quite comfy.
I like and appreciate all the cars, as long as they're $1500-$4000. I refuse to buy a daily for more than $5000. But I'd probably find something to love even about a Pontiac Aztec or Fiat Multipla, if I ever owned one of those...