51-year-old Sosa sat down with ESPN for its new 30 for 30 "Long Gone Summer" and was pressed on if he'll ever "come clean" about his alleged PED use during the famous Home Run Chase, as Chicago Cubs owners have long hoped he will.

Sosa cracked a smirk and said, "What do they want about me when pretty much everyone in that era did it?"

When pressed again, Sosa laughed uncomfortably and added, "I'm a very happy person, my friend. I'm good, I'm happy. Know what I mean?"

"There is about 4 or 5 [players from that PED era], maybe more than that, in the Hall of Fame. So, am I the one to blame?"

It was pointed out in the doc, Sosa has denied using steroids and other PEDs in the past -- even doing so before congress in 2005.

Reporter Paul Sullivan pointed out ... "there is no smoking gun" to prove Sosa did cheat.

"The only proof is the New York Times story about the leaked voluntary drug test. But, even that one, who's seen it except the NYT guy?"

Still ... COME ON!!!

Even 56-year-old Mark McGwire has come clean about taking PEDs ... and says in the new doc, "I regret doing it."

But, not Sammy. He's digging in his heels.

"A lot of people say different things, different opinions but I can say to you, what Mark and I did in '98 was incredible."

"Doesn't matter if we're never going to make it to the Hall of Fame, but that's okay."

"I have a peace with God. I'm happy. I've got my family. I've got my granddaughter, I'm good. but I believe what Mark and I did in 98, definitely, we shocked the world and I do not think something like that will happen again."

As for McGwire, he called his use of PEDs "stupid" -- but claims he only really used 'em to help recover from injuries ... not for the added power boost.

McGwire finished that season with 70 home runs. Sosa finished with 66.