When our oldest son turned 3 we got him a V-Smile system that hooks up to the TV. He loved it! Believe the age ranges on the games - those listed as 4-6, etc did frustrate him at that age because they expected him to recognize lower vs. uppercase, basic addition, etc. At age 4, he got the pocket V-smile which plays that exact same cartridges - still going strong.
Our youngest son, 3, now plays the V-smile and occassionally our oldest, now almost 6 still plays. We have 12 games and it has been a good investment. And get the AC adapter for the TV version and rechargable system for the the V-smile pcoket (2 years and still charges very well!). the systems are used daily in our house
As far as the system shutting off, games not playing, etc. I found a fail-safe solution. Keep alcohol pads (like those for shots, like $2 at a pharmacy for 50) and clean the catridge everytime you change. Works like a charm!