Haven't seen them in years, but I remember thinking King Solomon's Mines with Richard Chamberlain wasn't bad. Same kinda thing; it felt like a Raiders rip-off, and the poster/box covers confirmed that that was exactly what the studio was hoping, but I still liked it well enough.
Although keep in mind that I was only 12 or 13 when I saw it... it came out in 1985 and I haven't seen it since. It had a sequal; Allan Quartermain and the Lost City of Gold I think was the name. I don't remember thinking that one was as good.